In terms of plugins for some quick mastering, I'll usually use the URS Mix EQ, followed by the URS Fulltec(sometimes, really only if the low end needs some non-muddy beefing up), then followed by either the SSL Master Compressor or the Voxengo Polysquasher, then into the Waves L2.
For my preferred mastering chain at the studio (instead of doing it ITB) with outboard, it goes as follows(of course, sometimes certain pieces aren't needed, and others are, but these are the usual suspects):
Lavry Blue Series D/A
GML 8200 EQ (for the surgical stuff)
API 550 Mastering Version (for the mids mostly)
Avalon 2077 OR Manley Stereo Pultec EQP-1A (for softening the high end and tightening the lows)
Manley Vari-Mu (used around half the time)
Crane Song STC-8
Waves L2
Crane Song HEDD 192 (without the HEDD processing)
The studio where I use this gear is mainly a private mix place, so the room doesn't sound the same as mastering houses, but it definitely doesn't sound bad, and the gear is great.