Nubby sippy cups are all BPA free. They are also really inexpensive, so durable and have a hip design. We've been using them for a couple years without leak issues. They also don't have removable valves so there aren't parts to keep track of. They come in several styles of tops depending on the preference of your child too.
I did want to make a comment about the sigg cup. I used to really like the Sigg, but they're made out of aluminum which is actually a toxic metal. People are all in an uproar about aluminum in deoderant, but i haven't seen too much about aluminum in other things too that completely leach into our food and drink (ie, cups, cans, foil, etc.). Just FYI. At least the Foogoo cup is stainless steel. We have one of those too, for warm drinks and haven't had a problem with it leaking.