Although there are strict rules around what investments can be held in an individual savings account, for adventurous and experienced investors there is still a surprising amount of choice.
Catherine Penney at Barclays Stockbrokers said: "While many investors use their Isa to access mainstream equity markets such as the UK, US and Europe, an Isa allowance can be used to access less well known markets such as Australia or emerging markets including China, Brazil and the Philippines."
But investors do not have to restrict themselves to regions, or even shares. Ms Penney explained: "Those who are looking to diversify away from equities and are comfortable investing in commodities have for some time used exchange traded funds (ETFs) to get exposure to gold, silver, copper, but also oil, foodstuffs and even forestry.
"In fact increased interest in global warming and alternative energies has led to people using their Isas to invest in alternative energy."
Ms Penney warns that as with all less obvious or less mainstream investments, investors need to understand what their Isa money is buying.
She said: "As with all investments the value can fall as well as rise and investors may get back less than they invested. However, when diversifying away from mainstream equity markets an investor should make sure that they understand the underlying dynamics which may impact commodities or emerging markets."
Commercial property funds may have taken a battering, but lack of supply and increasing demand have kept residential property prices fairly stable or – in some parts of the UK – even increasing.
The Government says the UK needs to build 750,000 new properties of all types by 2025 to meet demand, but this is a target most property commentators believe is unlikely to be met.
Becoming a buy-to-let landlord is one way of cashing in on the residential property shortage, but it also involves admin and upfront expenses. Instead at least two fund managers claim to have come up with an Isa-friendly solution for those wanting exposure to residential property, but without having to deal direct with rental voids or noisy tenants.
The TM Hearthstone UK Residential Property fund buys up professionally managed properties and has a benchmark to exceed the UK House Price Index across England, Scotland and Wales.
Castle Trust has launched two structured products which are Isa-ready: the Income HouSA which tracks any rise or fall in the Halifax House Price Index, and the Castle Trust Growth HouSA which offers a gain of between 1.25 and 1.7 times any increase in the Halifax index or a loss of between 0.75 times and 0.3 times any decline.
Even so, investors need to have serious faith in the residential property market before using their Isa allowance. Danny Cox, an adviser with Hargreaves Lansdown, said investors had to ask themselves if they believed housing would perform better than the stock market.
Mr Cox also pointed out that while average prices may still be rising, they were nowhere near their mid-Nineties to mid-Noughties highs.
Another factor that investors may want to take into account is that the funds have only just been launched, so no past performance data is available.
While gold bars may not yet be "Isa-able" there are other ways to use your tax-free investment to buy into the rising, or even falling, price of commodities including metals, minerals and foodstuffs.
In institutional large-scale investing, commodities will often make up a small part of a portfolio as a hedge against inflation, which could degrade the value of mainstream holdings such as blue-chip shares. Using tangible assets is also a way of diversifying away from stock markets.
Adrian Lowcock, another adviser at Hargreaves Lansdown, said Isa investors could include commodities via exchange traded products (ETPs) – also known as exchange traded funds (ETFs) – in their Isa allowance.
ETPs use futures and other complex mechanisms to track the price of the chosen commodity. They are in essence not the commodity itself but an artificially created way of buying into its price.
Mr Lowcock said: "Investors can decide whether they want equities or precious metals such as gold or platinum, or agricultural products such as wheat or lean hogs.
"However, not all can be included in an Isa and ETPs such as those that are leveraged may be more volatile and risky. Others use futures to give exposure and they may not closely track the underlying asset."
Neil Jamieson at ETF Securities said investors could also use products such as ETFs to offset the impact of geopolitical events. He explained: "There are also tactical opportunities that more active investors can exploit in their Isas, for example the Arab Spring and oil prices."
Some investors also like to add exposure to gold in order to diversify away from equities and bonds.
Mr Jamieson said: "In an environment of loose monetary policy, investors are increasingly worried about the scope for flat monetary debasement and the return of inflation. Gold as a hard asset is perceived as a store of value. A further factor that is spurring investor interest is that the world's central banks are net buyers of gold – 419 tonnes in 2012."
Even so, commodities should be used sparingly. Mr Jamieson said: "I would advise most investors, particularly Isa holders, to look at commodities as a niche part of their portfolio, ideally no more than 10 per cent. If an investor has built up an Isa worth more than £100,000 they will have more to play with.
"Even so, commodities need to be included as part of a wider investment play."
The role of investors (or even taxpayers) in propping up large companies and institutions has become more transparent as a result of the financial crisis, with HBOS and RBS being prime examples.
Lending money direct to companies in order to generate a return used to be impossible for individual retail investors.
Bonds, issued by companies as a way to borrow money from investors by agreeing to pay back a set rate of interest in return, were until 2011 only available to large institutional investors, such as pension funds.
Retail investors wanting a piece of the action would have to invest via a collective bond fund – a basket of bonds bought on their behalf by a fund manager.
But since 2011 investors have been able to buy individual bonds, known as retail bonds.
Mr Lowcock said: "These are also known as individual corporate bonds. Large companies such as Tesco and Severn Trent Water have issued them as well as some charities like Mencap.
"In fact only last month buy-to-let lender Paragon also issued one."
Retail bonds pay a set rate of interest, at the moment somewhere between 4 and 6 per cent, and the risk you take is the company going bust. Larger companies such as Tesco may be a better risk than, say, Leon, a healthy fast food chain.
"Of course you may have to invest for years – five or 10 or 20 years – but there is a secondary market where you can sell on your bond, although it may not be at the same price you bought it," Mr Lowcock said.
He said investors should expect to invest at least £1,000 and pay stockbroking charges – a fixed amount per bond. There will also be upfront fees to be paid.
Case study: Taking a risk but with safety nets
Philip Chapman, a 42-year-old sales director, lives in Stony Stratford, Buckinghamshire, with his wife and two young children.
"We opened a Vantage account with Hargreaves Lansdown a couple of years ago to consolidate all our Isa and pension savings.
"We bought into 14 funds and a year ago we decided to take a bit of risk with some of our savings.
"I researched commodities and came up with the Artemis Global Energy fund. We invested £2,000 in the fund, and although it dropped in value it has since made some gains," says Philip, pictured. "I'm a believer in not having all your eggs in one basket. It's a higher-risk fund and we knew this, but with the economic and political situation being what it is, having a fund with a long-term view gives our savings not just some added interest but the chance to make some money in the long-term.
"We intend on staying in the fund for some time. We also try and use our tax savings allowance most years and our Isa is our reserve account. Our savings are up 30 per cent since we opened the Vantage account.
"Most of the rest of the portfolio is in construction-related stocks, which I consider a less risky bet."