Got an hour or two to spare? Well rather than slouching in front of the telly, you could do some work - and get paid for it.

Several websites have sprung up that allow people to sell chunks of their time to employers or to bid for contracts online. This means you work when it suits you - which is particularly useful for working mums and dads.

How does it work?

Traditionally, in part-time work you have to commit to working a whole day or at least half a day. By contrast, Slivers-of-Time allows people to sell their time to employers in blocks of two hours or more. You post your CV and state your availability on the site and businesses can book you to fill a gap at the last minute, to cover busy periods or to undertake a specific project. The work can be anything from data entry and administration to telesales, conference preparation, marketing, care work and catering.

This is a good way of selling your specialist skills and suits those who are fed up with working long hours in the office and being under a lot of pressure. It obviously suits families but also anyone who wants a different lifestyle. Very often women struggle to find the same kind of work they did before they fell pregnant, and this might be a gentle way back into the jobs market.

Apparently, 7 million people want to work flexible hours, according to Cambridgeshire Slivers, which is managed by Anglia Ruskin University's Employment Bureau. The problem is that there is too much demand from people craving flexibility - and not enough employers who have signed up to the service. It is currently limited to the Cambridgeshire area. But there are signs that demand is picking up. Smaller companies in particular have embraced the system.

There is another site, PeoplePerHour, where freelancers can bid for work - for example translation, copywriting, web design or other IT work. When I looked someone was looking for someone to translate a divorce certificate from Spanish to English for an unspecified fee, and an educational consultancy wanted a logo for less than £250. The jobs on offer change all the time. This page explains how it works.

If you are in full-time work, here is some advice from the government on flexible working. In April the statutory right to request flexible working is being extended to parents of children aged 16 and under.

But the flipside is that as more and more people freelance or work part-time, they don't get any of the benefits that come with a full-time job - paid holiday, a pension, health insurance... For employers the advantages are obvious - they save money with a casual workforce.

Still, it's nice to know that you can sell your free time to an employer to make some extra cash when the money is tight - or when you fancy a holiday or a new pair of shoes.