USB-based flash storage devices are the smallest removable storage around. They're about the size and weight of a disposable lighter, but they can hold from 8MB to 1GB of data. They don't need a separate power supply or batteries, and they draw very little power from the USB port, making them ideal for laptops. They're also fast, sporting transfer rates of more than 1MB per second. And their dimensions and ease of use make them great for shuttling files between work and home, giving presentations, or swapping MP3s.

Since these keychain drives were first introduced a couple of years ago, both hardware and software innovations as well as add-ons have made them more useful than ever before. Simple accessories, such as keychain attachments and clips, have increased their portability, and some include a USB cable to let you connect to a PC with an overcrowded or inaccessible back panel. Furthermore, security software and write-protection switches safeguard your data from unauthorized access or accidental overwrites.

Some innovations even extend the capabilities of the USB flash drive beyond basic storage. For example, the JMTek USBDrive Professional can act as a complete e-mail client, letting you send and receive e-mail from any computer.

Considering the range of designs, capacities, and capabilities, you'll find that choosing the right USB flash drives involves more than just buying the most megabytes for the money. We took an in-depth look at seven such devices, each with its own distinct strengths and weaknesses. Any one of them would fit in a pocket; read on to find the one that's a good fit for you.