Not that my stuff is worthy, but I've been digging the results (usually) from playing around with the PSP VintageWarmer plugin on my home recordings
http://www.pspaudioware.com/indexen.html
I have the early version, not the just-released VM2.
Its essentially a multiband compressor/limiter that seems to beef up and round out individual guitar tracks quite well, but also (using different presets and settings) can create the sort of "big sound" you're talking about when applied to a master track/late stage mix. I've never tried the (I guess standard) technique pc mentions of just applying an overall wash on an already bounced mix. I tend to do it all at once as above.
When you play as slow as I do, dynamics are your friend... but used in moderation I like the overall sound better when I kick this thing in. 'Course some presets can flatten it all to a uniform roar too.
Keeping in mind this is a 128K bitrate mp3, and that I didn't do any tweaking of the mix to create this example, here's a JamZone track from last summer with and without. I just plunked down a "light multiband compresser limiter" preset on the master track. One thing it did was exaggerate the reverb on the lead a bit too much.
WITHOUT PSP Vintage Warmer:
http://www.soundclick.com/bands/song...songID=4173840
WITH PSP Vintage Warmer:
http://www.soundclick.com/bands/song...songID=4913546
Probably proves the Pro's points, actually...