I just downloaded Skype so I could co-op game with a friend. I don't plan to use it much and was blown away by its 120MB resource usage. That's ridiculous!
After a bit of searching, I found Skype_3.6.0.244_Lite. I had to extract the files and run the installer. It looks like an old version of the software or something, kinda like MSN messenger before it was LIVE Messenger.
Anyway, this one initially takes up about 25MB+ of RAM. After minimizing it and letting it run idle, It's been slowly freeing up memory and after just 10 minutes, it's down to 9MB of RAM usage.
Unless there's an explicit problem with this version of the application, I'm going to stick with it for sure, as it suits my needs.