This is the best topic. I've given so much advice to my friends about picking the correct golf ball for them with no avail. My friends don't believe in golf balls and just play with whatever happens to be found in the nearby rough/woods.
I'm a big fan of the tour balls because I can generate a ton of spin around the greens and the feel I get from them off my irons is amazing. However, they cost upwards of $30 a box/dozen.
Last year, I had a very drastic dip in performance and decided to get back to basics. I went out (after I had lost all my expensive golf balls) and bought a $20 box of Taylormade Rocketballz. Last year's model had green numbers on them with the "Rocketballz" writing on them. I can't tell you how much I love this ball. It feels great off the driver, has little spin off of it, and gets absolutely launched. I used to be a DT Solo/NXT Tour ball player, but I've definitely switched to the Taylormade balls. Taylormade has done such a good job with R&D; in developing their technology for golf balls, its pretty impressive. I would highly recommend the Rocketballz ball. At $20 a box, its hard to pass up since it is a great ball for beginners and experienced golfers.
On the other hand, if you're an experienced golfer looking for a little more performance out of your golf ball, I would also recommend the Taylormade Penta TP3. Its a great 3 piece ball that generates little to no spin off the driver, large spin off the mid to long irons, and even greater spin off the short irons/wedges. It feels soft off the impact which feels great. This is last year's ball as well and most places (DIck's, Golf Galaxy, Golfsmith) are selling it for $20 a box as well.
I currently use the Taylormade Lethal 5piece ball, but if I'm ever in need to go back to fundamentals and use a round to just get my swing mechanics back, I will always revert back to a Rocketballz or Penta TP3 ball.