Here's my list:
For straight D&D style figs no one, and I do mean no one, does it better than Reaper.
I-Kore's Celtos line is perfect for any Slaine campaigns. They also make some of the best dwarf figs going.
Rackam: They are really expensive and they are fairly brittle, but they are hands down the most detailed metal figs on the market. They are 30mm figs, just a hair bigger than most other companies, but when they look as good as they do, who really cares?
Privateer: I just bought 5 of their Iron Kingdoms figures and they are top notch. They're not the standard fantasy fair, but if you like the artwork from the IK books the minis will not disappoint.
Fenryll: Their figs aren't pewter, they're made out of high cast resin. It's a little funky when you're used to metal. Their figs a little bigger than most as well, but they have some excellent figures in their lines, and the price is pretty good for what you get.
Mage Knight: If you remove them from their clicky-bases, some of the figures in the line are actually quite good. The new booster set has some great figs in it.
D&D Minis: They may not look great all the time, but for the price this is the best deal in minis. There are a LOT of places that sell singles, so not wanting to deal with random packaging isn't that big of a deal nowadays. (This goes for Mage Knight as well.)
I would mention GW, but aside from some of their more expensive figures (Daemon Princes and Greater Daemons for instance) their figs are too static for the price. Plus, they have one of the WORST online order businesses in the industry. Plus, their customer service is just as terrible as well, so when they screw up your order you'll get even more angry when you try and get the problem resolved.
Kane...I'm a miniaholic, and I really don't want help!!!