* Multiple simultaneous downloads
* Smart bandwidth usage
* File level priorities
* Configurable bandwidth scheduling
* Global and per-torrent speed limiting
* Quickly resumes interrupted transfers
* UPnP support (WinXP only)
* Supports popular protocol extensions
* Localized to different languages
* Typical memory use less than 4 MB
* Incredibly small: 94 KB
http://www.utorrent.com/