Ever wondered how much memory a program needed? Install the "time" package:

$ /usr/bin/time ls
[...]
0.00user 0.00system 0:00.00elapsed 0%CPU (0avgtext+0avgdata 4000maxresident)k
0inputs+0outputs (0major+311minor)pagefaults 0swaps

Unfortunately the "time" bash built-in makes it necessary to use the full path.

Thanks to youam for the tip.

Update: aba notes that calling \time works as well. Thanks!