I went through the same thing a couple of weeks ago; though I didn't have as much data as you. Mfenn is correct, you have to be careful about cloning the disk because the alignment will be off, which will seriously hamper SSD performance. Some tools can compensate for this, I used True Image 2011, which will correct the alignment if you restore from an image (but won't work if you use the cloning tool). Below are the steps I did, but I had several old hard drives I could temporarily backup data to, ymmv:
1. Used True Image to make one complete backup image on a spare HD, just in case things went horribly wrong - I could start completely over like nothing happened
2. Move data files (documents, pictures, videos, etc.) to a spare HD so I can copy over later
3. Cleaned up my OS by uninstalling programs I don't use anymore, clearing out temp files, disabled hibernation (the hiberfil.sys can be several gig, and you don't really need it in a desktop with an SSD). After moving my data files off the drive and cleaning up the HD, the total data size was ~65GB, plenty for the 120GB drive.
4. Made a disk image of my new "lean and mean" OS.
5. Shut down computer, and installed SSD in place of HDD.
6. Booted using the True Image boot CD and restored the "lean and mean" image to the SSD. True Image recognized the SSD and automatically used the correct settings for partition alignment, but I double-checked everything.
7. Booted into Windows on the SSD, once I made sure everything was working, I plugged in the old HDD as a secondary drive, formatted it, and moved my data files over to it. I then linked the "My documents", "My Videos", "My Pictures" folders in Windows to the appropriate folders on the secondary drive.
That was it, my computer was up an running. It ended up being a lot easier than I thought it was going to be. One last thing to double-check, you need to make sure that AHCI is enabled on your system and Windows is setup to use it. If AHCI was enabled during your Windows install (mine was), you're good to go. If not, there a registry hack you have to do to get it to work.