Ampeg SVX! I love this plug, can't imagine life without it.
I know some bass player/engineers that swear by doubling or tripling parts each with different eq's and usually a touch of distortion.
Also try parrallel compression. This seems to be my answer for every post but it works dammit! Learn this.
Hmmm what else...If I'm looking for fullnes in my bass I reach for R-bass or Maxxbass, both will add lower octave harmonics that will really fill out that ass end.
What am I missing? Ah yes, VST layering. If you have a synth modeler and you're musical enough to know what notes you're playing, you can always pencil in something to layer underneath your bass line, giving you infinite options for texture. Sometimes I use my mini moog to add a sub bass line beneath my riffs. This works great for hip hop if you want deeeeeep lows with a human feel, it sure puts rock in percpective as well, for instance, the chorus to Seven Fold's "Almost Easy".
Hope this helps.