I use JP Cycles & Dennis Kirk quite a bit. JP is in Iowa & I'm in Minnesota, so shipping times are typically 2-days or so. Otherwise, Amazon & eBay are popular. I dislike eBay in general, but Amazon has given me some really good buys, especially for cleaning items & clothing.
Yup, if you can't source stuff locally, for gear, I like Revzilla.. Free shipping for most stuff and they pay for the stuff to be returned to them if it don't fit.. Really friendly customer service... Never had a single issue with them.
Bought a couple of tires from them.. One broke free during shipping.. Called customer service and they shipped out another tire the same day.. Gotta love that.
Motorcycle superstore is great, but I find their tire prices to be a tad high. Otherwise good prices on most stuff. The rider's points is nice and meant to keep you coming back to them, but it helps now and then. Bought my helmet, jacket, air cleaner, tires, exhaust, windshield, bag and a few other items from them all trouble free transactions.
RockymountainATV has great tire prices and usually free shipping to go with that.