To be honest, with the way SSD prices have been falling over the past few months, the best bang-for-buck drive is going to keep changing. There was a combo deal for a 120gb Agility 3 + 550 OCZ PSU for only $88 after discount code and rebate on newegg just yesterday. Assume a resale price on the PSU at $40 (which is a very fair praice), the SSD would have costed only $44. The 128gb Crucial M4's and Samsung 830's have been hitting right around $100 as well, while the Vertex 4 is just barely more expensive coming in around $110. While more expensive, these drives are notably faster than the Agility 3, and with the track record of Sandforce controllers, could offer a much better bang-for-your-buck over Agility 3 and Vertex 3 drives. Have they fixed the so called issues with those controllers? They say they have, but there are still reports coming out with fair regularity of failing drives. That's why one person's best bang-for-buck may not be someone elses.
There is no single best option; instead, I would tell you to choose a maximum budget and wait for an SSD to fall into that price range. I like the M4 and 830 because of their high reliability and speeds compared to everything else. I paid $90 for my 64gb 830 for my desktop last thanksgiving and I love it, but with the price of SSDs steadily falling, I may make the jump on a <$150 256gb M4/830/whatever is out around this thanksgiving again as well.