After tracking through a DI, I usually end up rolling off a bit of treble (shelving filter starting at about 8 khz, roll off to taste) in a mix, and adding a bit of compression. By a bit of compression, I actually mean a lot of compression, with a slow enough attack to let the initial transient through at full volume, then compress the snot (8:1 ratio or more) out of the sustained note, with plenty of makeup gain to make sure the note doesn't vary much and is as loud as possible. I'd give specific settings, but they all change depending on the compressor, and my current favorite is an LA-2A, which only has a switch and two knobs. Crank both randomly until it sounds huge, and you're good to go!
I haven't found any plugins that really sound great for bass, except for the plugin version of an LA-2A, which doesn't sound as huge as the real thing, but does in a pinch, and a good parametric EQ plugin, which can be found free or cheap. I use the Sonitus one bundled with Sonar 4 PE if I don't have a hardware EQ available in front of me, or to expiriment with before patching in a hardware unit to print.
If I can't get enough "push" out a bass doing the above, I'll dial in some bass frequencies at about, oh, 125-200 hz, with a narrow Q, and notch the EQ around the bass drum. This usually does it without muddying up the mix too much.
Notice, this is all for the DI only--as soon as I bring a mic'd amp into the picture the whole thing changes, depending on what sound I captured through the mic, and whether it actually made things sound better or not. Also, the above applies to what I like bass to sound like, in a primarily rock/metal setting, and doesn't necessarily apply to pop, super-clean smooth jazz, or accoustic music. It also doesn't take into account any EQ'ing you might do for your own bass tone--it's just what I do after recording someone else to give a raw track "life" before working with it.
Sorry for the length, but it sounded like you were asking for specifics, and I endeavored to give you some settings, as well as the philosophy behind them.