Shell:

curl -n -F "content=<-"  < file      (not binary safe)
cat file | curl -n -F "content=<-"   (not binary safe)
curl -n -F "file=@/home/user/foo"    (binary safe)

Client:

Development (git): http://git.server-speed.net/users/flo/fb/
Latest release: .
GPG sigs, older versions:

If you want to use authentication (needed for deleting) add the following to your ~/.netrc:

machine paste.xinu.at password my_secret_password

Packages:
Arch Linux: pacman -S fb-client
Debian:
Slackware: