Good lord, I really missed this boat didn't I? I'm not going to explain tags too much, but they're basically a Web 2.0 concept that's all over. Take del.icio.us for example, with its ability to use tags to help sort, identify, and search through links. MovableType has it built in now, and there's even a plugin for Mail.app called MailTags that adds it to your email if you're a mac user. I really dig this concept and over the next little while I'm going to be moving in that direction with a lot of my stuff.