New Yahoo! mail rocks the house
Just got accepted into the Yahoo! beta. This is the first web-based email I would consider using. If I didn't have multiple email accounts, I would probably switch. Differences from oddpost: 1)doesn't use a popup window, 2)Doesn't seem to have rss integration, which oddpost has (seems like an odd decision, maybe they want to save something for the sequel?).
I won't post screenshots 'cause you can see them here if you're interested.