move apps to sd card? defrag it?
Since the sd card is significantly slower than internal memory, and flash memory never needs to be defragmented, neither of those will likely solve any problems.
First thing to try would be clearing both the main cache and the dalvic cache. After that, uninstall any apps you no longer (or rarely) use, and again clear caches. If it's still running slow, do a full backup and then a factory reset to clear everything out. You can use AppExtractor from the market to restore apps and data from a nandroid backup. Restore one (or a few) at a time so you can spot which one may even causing the problem.