It's extremely easy to log into your N900's "terminal" via ssh. Could be done with Putty in Windows but on Linux it's just part of the system. I prefer "guake" as terminal on Ubuntu, it opens a window almost instantly on keypress.

Many of the shell scripts you might use on Ubuntu can be reused on Maemo. I love how I just need to write stuff once and can use it on different platforms with minor to no modifications at all.

If you install Python on your N900 many scripts/apps can be used there as well. It's quite easy to learn (thus quite popular). Ubuntu uses it extensively, and the N900 is great for learning the language (and others) on-the-go.