One of the best plugins out there is the Waves SSL Plugins. It recreates the Solid State Logic equipment to the T with a great sounding mixing board, compressor, and equalizer. Lots of well known bands have been recorded with this plugin including Muse.
The SSL E-Channel is probably the most useful out of the group since it handles the EQ, compression, and high/low pass filters in one unit. The other plugins in the bundle are great for single channels. SSL-G Master Buss Compressor would help maximize the levels on a kick drum, bass guitar, or snare drum. SSL G-Equalizer is good for fine tweaking vocals or guitars. It looks like they recently added a fourth plugin to the bundle called the SSL G-Channel, which is the mix of both the SSL G-Equalizer and SSL G-Compressor.
These plugins would be great if you like the analog sound to your recordings in a ProTools environment.
Right now, there is a sale on the Waves SSL plugin for 40% off until October 31, 2010! This brings the bundle price down to $465.00, which is the lowest ever.