An SSD is the single, biggest upgrade for a system that is running off a HDD. No other component upgrade can do what an SSD can do. I can fully recommend a Samsung 830 SSD if you can find them, the new model is out and the 830's are going fast!
Do a clean install of Windows 7 on the SSD and put drivers
and updates on it and then install your programs. Anything other than that needs to go on the HDD.......ie the User's folder, any music/pictures/documents/videos. Get rid of your hibernation file as it usually reserves quite a bit of space. Adjust your pagefile and system restore to something a little more reasonable as well. That should have you taken care of!