We're really fortunate here in Indy - the 'plant guy' at our local LFS is a walking encyclopedia when it comes to aquarium plants. It's mind-boggling the amount of info this guy can throw out on anything you ask him in regards to a plant, and he stocks a really good selection of stuff.
The only thing I had that was off the beaten path as such was one, Limnophila Sessiliflora, which I really love but I'm thinkin' I'll skip for this scape. The other was minI pellia / coral moss, which seems to be a bit harder to find than just walking into a shop. At least yet.
Who do you buy from online? Wouldn't mind having a good source in tow.
Buceplant.com, though I don't think any of the plants they stock will be going into your tank. It's worth a look though, I absolutely love everything about them haha.
Amazon, aquabid and eBay should be decent places too.
Aquariumplants is also a place some members use, though I personally haven't bought anything from them.