I use Intel Smart Response SSD caching on my work PC - 1 x 500GB HD and 1 x 60GB SSD as cache. (I think you can set this up to cache multiple drives but you might need one SSD partition per HD.) It was a little fiddly to set up but since then that it's been trouble-free. It was not expensive to buy the parts and it does a good job of balancing the competing requirements of disk space, performance, cost and general hassle.
Flat-out performance is a little ropey by SSD standards, but random accesses are fast, so it mostly feels SSD-like. (I have the system set to write-back mode, so write speed is decent too.) Of course, as with any cache, it is possible for it to become filled with inappropriate data, or for a data set to exceed the size of the cache, but for my purposes (mainly building C++ and running the result) I've found it to do a good job. With a 60GB cache I've found these situations pretty rare day to day anyway.
(Smart Response is Windows-only; I don't know how it compares to the Mac OS X or Linux equivalents.)
Flat-out performance is a little ropey by SSD standards, but random accesses are fast, so it mostly feels SSD-like. (I have the system set to write-back mode, so write speed is decent too.) Of course, as with any cache, it is possible for it to become filled with inappropriate data, or for a data set to exceed the size of the cache, but for my purposes (mainly building C++ and running the result) I've found it to do a good job. With a 60GB cache I've found these situations pretty rare day to day anyway.
(Smart Response is Windows-only; I don't know how it compares to the Mac OS X or Linux equivalents.)