Wirelessly posted (HTC Diamond: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.11) Sprint MP6950SP)
I also suggest using ClearTemp regularly.
Follow rhacy's guide in his first link and I bet you'll be surprised how much memory you can free up.

He covers all the bases very well so I really don't have anything to add to free up more memory other than using a tool like UPX4PPC to compress exe and dll files. I'm experimenting with this now and it does free up a little more space but you can't compress everything because some things don't work right.