You use Firefox don't you? If you use the web interface to post and have Greasemonkey installed you can use this really, really nifty script by afuna (Taglister (http://afuna.theblob.org/greasemonkey/)) that makes all the tags you've ever used appear below the entry box and you just have to click on those you want to use. I would never be able to keep track of all the tags I have if it wasn't for this script.

Ooops! Sorry for the bad coding!