Gmail and Opera Mini on the phone!
A couple of months ago I found the new Gmail mobile application. It's a clean small Java application that one downloads to the mobile phone for accessing the Gmail account.
The application has easy access to almost all of the features that the ordinary web interface has. There was (and probably still are) an mobile version of the web interface but it didn't have the easy access to all the different menus as this application has. I really like it and use it several times each day.
Another cool little application is the Opera Mini browser. These a full feature list here. Basically it transforms the pages so that they fit the mobile screen, and it's fast! It also has some special features for navigation on small screens. And it supports RSS bookmarks!