Papyrus - absolutely necessary replacement for the built-in calendar and to-do list; great interface and feature-packed

Windows Live Search - decent interactive mapping application with street maps, satellite imagery, and real-time traffic updates, but a confusing UI

Virtual Earth Mobile - another good interactive mapping application; faster than Windows Live, and an easy-to-use driving directions feature

Google Mail Mobile - nice fast interface to your gmail account

Working around e-mail issues

I didn’t realize how good I had it with e-mail on the Sidekick.  Windows Mobile e-mail requires an incredible number of clicks to do anything useful:

No way to delete more than one message at a time

Could not get it to leave POP messages on the server

No auto-complete on e-mail addresses; have to do a lookup

No way to force it to always download the entire message

Deleting a message in mail also deletes it on the server

However, I did figure out a workaround that was somewhat usable while I was on the Dash:  I set up a fresh gmail

account, then configured my other gmail account to forward a copy of any incoming e-mails to it.  Then, on my Mac, I set up a filter to forward any Yahoo! e-mail to it as well (because, inexplicably, Yahoo! won’t let you both POP and forward from the same account).  That way, I was able to get all of my e-mail on the Dash, and could delete it as I saw fit without worrying about deleting my original copies.

All that said, I kept the Dash for quite a while, although I recently sold it on eBay for the iPhone ...