gsendfile is a frontend to the Unix tools sendfile and receive. Unlike FTP, sendfile (and the saft protocol), allows asynchronous file transfer via the Internet (similar to e-mail). gsendfile lets you browse your inbox and send, store, preview, and delete files/archives. It also allows you to add people to a list of contacts, making it easier to remember their logins and hostnames.
MLAutosearch is a shell script which is good for searching for rare files within multiple P2P networks. It uses the mldonkey utility to carry out much of the work. It reads a file named "slist.txt" which contains mldonkey search commands and starts a mldonkey search for each line in the file. It will download the first file that matches the search, and then will remove that search string from the list. When it reaches the end of the list, it begins reading it from the beginning again. MLAutosearch will download up to 3 files simultaneously.
Credence is a tool for combating spam and pollution in filesharing networks. It lets you vote on files in the network, analyzes the votes of your peers so that you can avoid polluted files, and automatically identifies the voters in the network that are most credible and useful. It is built as an extension to LimeWire, running on the Gnutella filesharing network.