Before I got the iPhone, I was using a free service called
mail2web. They have a pay service, but you don't need that.
I would forward all my gmail to my mail2web address, and it would push it to my WM phone (Cingular 2125) via activesync. I could also set it to sync my contacts and calendar on the fly but I didn't often use those features (too much data swapping... email was good enough for me).
It did save my butt one time when I accidentally wiped out all the contacts on my phone AND in Outlook on the computer (frighteningly easy to do)... just resynced with the free exchange server and I had everything back. Phew!
Something tells me Google will offer this service free with gmail soon... just a guess....
Yeah, I'm looking forward to these features BIG TIME with the iPhone...