There is a lot of good funk out there, but I like to divide funk into three schools of thought. The first school, you have already discovered, and that's James Brown. It's fat, tight, and ruthless. Nothing is out of place, and IMO it owes much of it's sound to Motown, R&B, and the Funk Brothers with James Jamerson on bass.
On the other side of the spectrum is George Clinton. Start with Funkadelic, and the move over to Parliament and P-Funk. It's loose, super funky, and there are a lot of people in the mix doing their own thing, and it's all cool as long as everything converges on the one.
The third camp, kind of splitting the two comes out of New Orleans. This sound is funky, laid back, and it mixes and matches a whole lot of different influences, like RnB, Creole, Zydeco, Native American, Cuban, Blues, and Jazz. In New Orleans they throw it all in the mix and make you shake your **** with a smile. Start with the Neville Family, and listen to The Neville Brothers, but most importantly listen to The Meters, with George Porter Jr. on bass.
These are all starting points, and you'll discover a ton of stuff down each one of these paths, including crossover stuff from other genres like Jazz (think Miles Davis - Bitches Brew, and On The Corner) or even reggae (Toots and the Maytals - Funky Kingston).
Have fun
