I read in the press release for the S60 3rd Edition web browser announcement that AJAX was supported. To test this out I went to my Google Calendar in the browser on the Nokia E61. A dialog box pops up stating the browser is not supported, but to tap Cancel to proceed. Of course, I pressed the cancel soft key and lo and behold Google Calendar runs like a champ in the browser! I was even able to add events and more right from the browser. This is the only mobile device I have ever had success using Google Calendar and this type of feature just makes me happier and happier that I purchased the device at a very reasonable price, US$415.
UPDATE: I was asked for some screenshots so here you go. You will get warnings that GCal is not compatible with the browser, but pressing Cancel allows you to continue to Google Calendar. As you can see it is functional, but not optimized for the mobile device. It is usable too, but is a bit slow at times and I would really only use it for minor updates and to see what is on the schedule. It can be very helpful for viewing the schedules of family and friends though. Here are some thumbnails below. You can also visit my Flickr page for larger shots.