Windows 7 is pretty well optimized for performance to begin with. I'm sure there are a few programs out there that might help, but I've found that unless you're looking for specific improvements, it's best just to leave things as they are. It's not like the old days where Windows 98 was horrible at managing resources.
Anyway, your best bet for improving performance in the long run is by doing the following:
A) Use a program such as CCleaner to clean out temporary files and other information that isn't necessary.
B) Install Windows on a separate hard drive and/or partition so that your computer can access files easier. If using one hard drive with separate partitions, it's best to have the Windows partition in the front of the hard drive's space. The best solution that I know of is to buy a smaller (40-80 GB) solid state drive and use that as a system drive (Windows, Programs) and install everything else (Games, Media, Storage) on conventional drives.
C) Run a disk defragmenter regularly. I run mine once a week because I tend to fragment files often. You should also run any other system maintenance programs you have.
D) Keep your anti-virus and anti-malware/spyware programs up to date. The most common setup is the following: Anti-Virus, Firewall, Anti-Spyware, Anti-Malware. It's best to use individual products in most cases, as the "suites" aren't quite as powerful as the best of the individual products. Personally, I use MSE, Comodo, SaS and Malwarebytes because they're all free. Make sure to run these programs regularly as well.
E) Uninstall any large programs that you don't use often. Also, remove as many items from system startup as you can. This will cut down on the programs running all of the time and will therefore leave more resources for the active program(s).
F) Along the same lines as the last point, remove/turn off any Windows Features and programs that you don't need. Most of them won't bring too much of an improvement, but collectively they'll help a bit. You can access the Windows Features menu by going to the Programs & Features portion of Control Panel and clicking on Turn Windows Features On or Off.
If you're looking to improve performance on a large scale, your best bet is to upgrade your hardware. In that case, there are many threads in this forum that can point you towards budget hardware that works very well.