I've purchased from a seller called apethouse on ebay and I was very satisfied. They sell malaysian driftwood. The pieces were solid, clean, and sank immediately with very little tannin leaching. The first couple pieces I pre-soaked, but eventually I just started putting them directly in the tank with no prep at all. They have sales for a piece as pictured, or lots of a size category where they pick the pieces. The only downside is the shipping is pretty expensive, as this stuff is pretty heavy.
Foster & Smith also sell malaysian driftwood, but they send you random pieces from whatever size category you pick. Good if you want to combine a bunch of different pieces, not so good if you're looking for a big centerpiece with a particular look. However, their flat rate shipping can make it a bargain if you're not picky about the pieces you want.