What does everyone use for finalizing their mixes (leveling, max loudness etc)?   I have played with Sound Forge's wave hammer for my mixsets to just level everything off and give them a good level of loudness but I only had the demo and am looking to find either something free or something to purchase.

I run mine through a highpass filter to kill any extremely low bass patterns (which usually happen during mix points) and a multi-band compressor to smooth things out, finally a little peak limiter to give it that even volume.

I'm with Matt. I always run it through a high pass AND a low pass (so I don't blow your puny car speakers up) then a Multiband compressor and then the L2 Limiter.
Waves products are expensive and obviously they'll break a small amateur hobbyists bank account. But they are WORTH it. SO good.