Oh duh, I'm such a fool.
1. I have been sending myself notes - things to read, ideas to remember, etc - in the form of e-mails for a year or two now, and always forget to go back through my inbox/drafts folder to find out what I was supposed to catch up on. Functionspace clash - my inbox is not my to-do list. One procmail rule and one extra folder later, et voila, a separate folder for notes. Duh duh duh.
2. I've vaguely thought of tying together my webspace with my mailspace, allowing me to access either with the other, but been put off by the terrible thoughts of using an IMAP protocol in Perl. Only just now have I realised that my mail is stored in flat text files, one directory level above my webspace, and will be a piece of wee-wee to access/convert into webspace. Integration just got a whole step closer, without me having to do anything :D Some performance and security issues may need to be considered, obviously, but no reason why I can't just e-mail myself and have it pop up as a list on a website now - instant blog!
Could do some kind of archival filtering/splitting thing using another script, and go from web->email by adding a few headers. Nice.
3. ... or even start implementing a FOAF directory structure as some kind of nested hierarchy, to coincide with my nested e-mail folders. A quick directory-crawling Perl script should be able to bundle it up into one rdf file/actually generate the xml, unless I can do it straight in rdf, or something.
4. Probably quite easy to knock up something in XUL that allows me to save messages in the folder they're already in, rather than the default "Drafts" folder. Then, Mozilla mail client is my editor...