I have a MacBook Pro A1260 from 2008 and I want to upgrade to the fastest SSD I can get, as long as the rest of the system isn't the I/O bottleneck.
Where can I find information on compatible SSDs, and how many MB/s my system can handle?
Everymac.com is as close to a comprehensive source of system information as you'll find. In the case of your Mac, you can see it has a 1.5Gb/s SATA interface. So you won't be able to get the full potential sequential transfer speeds of a recent SSD, but keep in mind that the most noticeable benefit of an SSD comes from the random access speeds, which are less likely to be bottlenecked by the SATA interface.
It's also worth considering that SSD prices have come down a lot lately, so you're less likely to save much by getting an older model. I'd recommend looking at the Samsung 830 series or the Crucial m4. Both have excellent performance and good reliability.
Supposedly almost every SSD should be compatible with your Macbook Pro. Most SATA III SSD is also backwards compatible with SATA II. Even if you won't get the full benefit of the SSD by having a SATA II interface, but it will still be way faster by traditional hard drive.
However I may just be a really unlucky guy. My late 2008 Macbook freezes occasionally after I installed SanDisk Extreme SSD. After getting a replacement SSD, reinstalling OS X a few times, resetting PRAM, enabling TRIM, and so many other things; I was convinced that my laptop is not really happy with the SSD itself. It was kind of confirmed by reports by a few people.
So I guess the best advice I have is see if other people has problems before buying the SSD, and then if you still decided to buy it, have a plan B of what you're gonna do if it doesn't work.