USB keys remain popular, and there really is something for everybody. From those that are the size of a thumbnail and no thicker than a credit card to virtually indestructible waterproof models--not forgetting those that double as memory card readers, too.

Capacity, speed and accessories

The size of USB keys just keeps on growing. Today, the minimum is 1 GB, and the maximum is 16 GB or even 32 GB. But how big is big enough? In general, it would seem that 2 GB keys give good value for money, but it does of course depend on what you want to store on your USB key. If you're only going to be transporting a few letters and spreadsheets, then 1 GB will probably be enough. If you're carrying around bigger files, like photos and music, then 2 GB or 4 GB keys will be more appropriate. Finally, if you've got a Home Cinema system that has a USB port for reading DivX files, then you'll want at least 4 GB.

Once you know how much room you need, you need to choose the right key. The most important factor is how fast it can copy files. The most advanced USB keys reach speeds of up to 21 MB/s, while the least powerful can only manage 3 MB/s. In practice, that can mean copying a 700 MB film can take anywhere from 33 seconds on the fastest USB keys to up to four minutes on the slowest.

To stand out from the crowd, some manufacturers include accessories and extra features. There are also special applications to automatically back up your files to your USB key, or carry around your e-mail client and Internet favourites to use on any computer. There are also more traditional accessories, like USB extension cables or lanyards. A more recent trend is including music, movies or other content pre-installed on the keys.