Don't worry about the RAM being used up, that's what it's there for. If you go into Activity Monitor and notice that for some strange reason that your "wired" ram is taking up almost all of your memory, then try a restart. But pretty much OS X is smart enough to replace the items in your memory with new items that you need quick access to.
I've read about people being worried about iTunes using all of their RAM. Well, if you have 2-4gb of RAM and iTunes wants to use 300mb to keep track of album covers while you browse the internet, let it. When you decide to open up Photoshop and do some work, if Photoshop needs the RAM for anything the OS will hand it over.