Glenn Gould is absolutely the definitive source in regards to Bach piano music. For me the beauty in Bach's music is the extreme technical expertise, which, like an extraordinary piece of architecture, unveils a perfect geometry and universal perfection that makes our hearts and minds meet in the same exquisite place. But you need an exacting performance to be able to appreciate it.
It gets so personal. Check out this thread just on Violin sonatas: http://www.good-music-guide.com/community/index.php?topic=20...
You just have to listen to a few of the best and listen and listen, and if possible go see some play live, and you'll start to know what you love and what you are looking for. I am a fan of period instruments and technical performances, rather than the more mainstream recordings by someone like Yo Yo Ma.
So some great performances that I personally love:
Anner Bylsma, Cello Suites on a Baroque cello
http://www.amazon.com/Bach-Suites-Cello-BWV-1007-1012/dp/B00...
Jordi Savall and Hesperion, The Art of Fugue
http://www.amazon.com/Die-Kunst-Fugue-Art/dp/B00005NTKF
(I love all their recordings and Savall does a mean Sainte-Colombe)
For Bach's Musical Offering I have a hard time saying which is the best: I have too many favourites.
Maybe just hit up Youtube until you find one that grabs you, but try and avoid anything that isn't in HD quality.
https://www.youtube.com/results?search_query=Musical+Offerin...
Savall does a fine version here: https://www.youtube.com/watch?v=Z4lwV3IMHMQ