There are quite a few monospaced fonts. Andale mono is bundled with a few MS
products. You can also find a monospaced version of Arial intended for use
with HyperTerminal, the Windows Telnet client. There are others bundled with
Corel products such as Letter Gothic (LettrGoth 12), Prestige 12 BT, and
Courier 10 BT. There are some bundled with certain printers such as Letter
Gothic supplied by HP.
Aside from that, Scriptorium's Onuava is worth checking. There are many
other interesting font there as well.
And among the not-free, commercial fonts: Font Font's Fago and Isonorm;
Linotype's ITC Avant Garde Gothic Light Mono, Montani, Olympia, Orator, and
Prestige Elite-just to mention a few.