I guess everybody with a laptop has experienced this problem at some point: You plug into a network and just want to exchange files with other participants. It always is a pain until you can exchange files with the person vis-a-vis.

Woof (Web Offer One File) tries a different approach. It assumes that everybody has a web-browser or a commandline web-client installed. Woof is a small simple stupid webserver that can easily be invoked on a single file. Your partner can access the file with tools he trusts (e.g. wget). No need to enter passwords on keyboards where you don't know about keyboard sniffers, no need to start a huge lot of infrastructure, just do a "woof filename" and tell the recipient the URL woof spits out. When he got that file, woof will quit and everything is done.
And when someone wants to send you a file, woof has a switch to offer itself, so he can get woof and offer a file to you.