This is a modification of THBMans excellent LastReadPost greasemonkey script, updated to store the read status on a central server for use on multiple machines. It’s quick and dirty and hasn’t been tested much, but so far seems to work. You’ll need a server with php and mySQL to use this.
FYI: I just added the ability to hide posts which have been read as discussed here. It's only in the server version and is controllable via the hideread var. It only hides posts on the more recent page, as I figure if you're looking at previous pages in the post, you're looking for something. It's kinda nifty, but I don't know how useful it is. I also hacked it in pretty quick, so there are likely bugs. I let my sub lapse so I can't respond in that thread, but there you go. --kitzke