Would you like to log in to a remote computer, start a long job (like recompiling your kernel), log out, and still be able log back in and see how the job is getting along? I did (although that made only 1 for 4 in my poll...), and that lead to finding the `screen' utility.
See this tutorial for a nice, easy intro.
For the impatient, you can start a screen with...
(suprise! :p), detach with
and reattach with
$ screen -r
Roughly similar effects can be achieved with the `nohup' command, which protects your processes from SIGHUPs generated by you logging out, but then it's harder to determine if your process exited successfully.