I'm not maintaining this package. Debian unstable has a working version of Bubblefishymon that supports Linux 2.6; it is also available here (though apparently not actively maintained). I repeat: please do not use my version, it's practically ancient.
This page features a patched version of Bubblefishymon 0.5, a WindowMaker dockapp that visualises your CPU activity, your memory usage and network traffic, and can also show a clock at your request.
I've added some Debian patches as well as my own patches that allow you to use it with Linux 2.5 and 2.6. You'll need procps v3 or later to use this version, though.