I've been looking for a compressor/limiter to use with my music which has a lot of adjustments available and sounds warm.
I tried out the stereotool one mentioned above in this thread, and thought that having as many options as it offers is awesome; and a multi-band compressor is an excellent thing to have, but somehow, I felt that the quality of the sound was not to my liking. It seemed like it made everything sound more digital, and any 'bad' sounds inherent to the mp3/digital compression were emphasized. Kinda harsh tonally. I tried EQing, and messing with the settings for a long time, but just couldn't produce anything that sounded good to my ears.
I like to use a program called T-Racks for my audio mastering when I produce. It's a VST that is quite powerful, and is meant to simulate tube rack-mount equipment. However, for my everyday listening, I wanted something that would be a bit more stable (ie a DSP meant to interact with a playback program like MusicBee, rather than a VST, linked through some bridging DSP which is one too many layers of complexity for me).
There is a DSP called izotope ozone made for winamp which is meant to emulate classic tube mastering equipment that is quite good. It has a pretty interface which matches up nicely with the MusicBee 'Dark' skin. Although it is not a free plugin, it is worth the cost if you are looking for something to use long term, which has a pleasingly warm sound and a lot of adjustable settings. I like to keep the room simulation bypassed (it's good for headphones though), put a gentle dip at 3.5kHz on the valve equalizer, bypass bass compression, about -10dB on the tube limiter, and some light tube saturation starting at about 5kHz. These settings give a nice analog sound with sufficient detail brought up through the limiter that you can listen to your music at a moderate volume and still hear good detail. The limiter is great to tame instruments that are mixed super hot too. Like most Miles Davis records--his playing has so much dynamic range that unless you turn it up loud, you just don't hear everything in the quieter parts of his phrases. A good compressor/limiter can remedy that.