The Piano gets its own section because:
A: It can be either an orchestral or band instrument.
B: There are lots of good free digital pianos.
C: It is my favorite instrument, so there.
One of the best pianos today is the sfz format Piano in 162 from Ivy Audio's Simon Dalzell. It is a Steinway Model B grand piano with five velocity layers, round robins, close and ambient mic positions and separate samples for when the sustain pedal is on or off. If that is all Greek to you, don't worry it just means that is has the features of a commercial library for free. Until very recently these features weren't available in a free piano. The only negative is that it doesn't have release samples, but you wouldn't want them for the ambient mic position anyway.
You can go to his website and either make a small donation and download it directly or torrent it (legally) for free.
Or you go to VSTBuzz and signup for free and download the piano directly for free.
Another great piano that was just released is the sfz Estate Grand Piano LE from Production Voices. It is a Kawai that was sampled on an estate in Canada. It has both pedal up and down samples and release and pedal sounds. You do need to sign up for their newsletter to get it.
A third fine piano is in the Sampletank 3 sampler pack. It is IKM's Steinway called the Grand Piano 1 SE. They don't give any stats for it, but it is over half a gig, so it has to have a fair amount of samples and it sounds good.
If you don't mind adventures in decompression, the Salamander Piano is a nice Yamaha C5 in sfz format.
I'm going to be egotistical here and point out a few pianos on my own blog. The City is a Baldwin with four velocity layers, the Iowa is a Steinway with three velocity layers, the Skerratt London is a lightly sampled Upright and the Whisper is an intimate piano.