I find the above posts, particularly Tubegroover's, to be excellent recommendations. I might add for an uplifting Baroque piece Bach's Brandenberg Concertos, particularly Nos. 4 and 6. Although it's not a great recording, the Archiv recording with Trevor Pinnock and the English Concert is my favorite performance of it, very upbeat and well-played. Also, check out the Correlli Concerti Grossi, with McGeagan and the Philhamonia Baroque on Harmonia Mundi--uplifting at times, relaxing at others, and a superior Peter McGrath recording, if I remember. Like Tubegroover, I find I can either relax to Mozart or get engrossed in it--it's funny how I might not initially feel like listening to Mozart, but once I start I'll spend the night listening to his music. I find it almost impossible to listen to Bach as background music, though, as it fascinates me and I wind up following all the musical lines. Another suggestion on the Suppe overtures would be the Mercury recording with Paray and the Detroit Symphony, I think, a very dynamic and well-recorded performance, though a little bright, as are many of the Mercs.
More Dumb "Classical" Stereotypes
As little as I know about "classical" music (in the Tower Records sense of the word) even I get bored and offended to hear people say "I LOVE "classical" music -- it's so RELAXING!!" Isn't more baroque music is played in coffee shops and dentist offices to "relax" people? I find Stravinsky quite fascinating and wonderful, but certainly not "relaxing." Whatever the distinctions or period confusion I have, I would love to hear your thoughts and recommendations for "classical" music that you find relaxing and conducive to concentration and/or happy "classical" music that fills you with energy and optimism. Obviously, a great recording would be an added bonus.