I order the majority of my equipment from BigAls (filters, dry food). They have the best prices on Tropica Master Grow, so I usually order a little extra to make the shipping worthwhile. I've never had a bad experience with them.
I order my live plants from Aquatic Plant Depot, but they don't carry all I would like to have. When I make another order, I will probably give Aquabotanic a go. I was not fond of that place with "wood" in their name. <--- /me avoids lawsuit
I also try to do my part by purchasing what I can, especially all my fish locally from the ma & pop places. I'm known well at the stores here--they treat me well, so I never hesitate to shop them first. I had a CustomSeaLife ballast go out that I bought there ($75 for a 55w PC). The owner just gave/exchanged mine for a brand new one--the whole kit--the last one on the floor! How cool is that?
I'm always looking for new places to buy from, and our sponsors will certainly be kept in mind next time I do some shopping.