http://m.gmail.com is the new mobile interface to gmail. Can't say too much about it, except in works on my Treo 600 - no muss no fuss. It's not fabulous, I wouldn't want to do much with it. But y'know it's gmail and it's available everywhere now. That's worth something.
I'm sure somebody is saying "but you have email on your Treo already. And I'm fairly certain that I do. First off, I've probably got some cruddy Sprint thingie I've never used. Second off, at one point in time I had it successfully communicating with my hiddenjester email - that might still work. HellifIknow. I can't remember the last time I tested that. Actually, I'm quite certain that send wouldn't work for that - I could probably read my email, but not send it.
Anyway, I know the web browser works, so setting up gmail as my "emergency on the go mail" is a nice thing.