It's not exactly what you're after, but the Safari Cookies plugin lets you "favourite" certain cookies, and everything else gets purged when you quit the browser or manually clean up.
Blocking known advertising crap via your hosts file might help too.
AdBlock as well as many others can be found here: http://extensions.apple.com
Interestingly, earlier I thought I had AdBlock, but I had a different one with a similar sounding name: http://sweetpproductions.com/safariadblocker/
I'm not sure about RES, sorry.
Maybe try a little app called DesktopUtility (scroll down to the bottom)? Are there other drives connected? Sometimes separate drives will have their own .Trash
folders.
hmm.. I'm not having this problem. I'm running Safari in 64bit mode, and my user agent is the default.
have you tried clearing flash cookies? I use Safari Cookies to clean those out... http://sweetpproductions.com/safaricookies/