If you have an SSD, Win 7 will detect it as such and 7's default behavior is to disable Defragmentation for that volume. If the installed SSD suports the TRIM command, then Win 7 will automatically apply same on an ongoing basis. Meaning, if you delete something from your SSD, then Win7 will run the TRIM command in the background by default and keep your drive running optimally.
This is different from Vista and XP - Defragmentation does not disable, and the TRIM command isn't natively supported for those OSs. You may download a tool to run TRIM on your SSD, but the OS won't do that on an ongoing basis. The User will have to manually run the tool from time to time. I should think that 3rd party disc utilities will (eventually?) implement Win 7's treatment of SSD's as their own defaults (i.e. detect and properly clean a compliant SSD with a TRIM command, but not run a defrag on it), but as of now I'm not aware of any available to the public.