Go online? I assume you mean web surfing, as some of the "other" things I do do involve being online.

Take notes with Xournal
Listen to mp3s with mpd/mmpc/mpc+powerlaunch
Run Windows apps on my Windows machine via RDesktop, SSH, and sometimes VNC
Dial numbers on my cellphone with phonelink/gnokii
Look at maps with Maemo Mapper
Playing games (mainly Tyrian and Powermanga, occasionally others, and probably soon fRaBs)
Reading PDFs (course notes, ebooks, whatever) with built-in reader/evince
VoIP with Skype
Spreadsheets with Gnumeric
Generally play around with a GNU/Linux system (not of interest to many, but it's a lot of what I do...)