I had to wait for this bit of software to come out of beta before I let it get close to my email, but MailTags 1.0 has been released. It's a Mail.app bundle which allows you to attach Spotlight comments to your mail messages. I've been making use of Spotlight to manage my research bits and pieces by basically tagging each piece of information that lands on to my computer - via email, pdfs, documents or even bookmarks. Then, when I want to search for that information again, I just do a Google-like search via Spotlight for the information I want. The missing piece in the whole scheme was the mechanism by which I could tag my mail messages. MailTags solves that quite nicely. You can assign priorities, due dates and projects to mail messages, as well as freeform comments. So now, when I do a search for "Florence conference", I get all the relevant material that I've collected together for this particular project. It's quite nifty, as all I do now is just leave various documents in generic bucket folders, and let spotlight do the fine-grained searching for me.