Here's my list
Spaz HD - twitter client, I'm not sure if there's anything out there for touchpad.
Facebook - this is for the wife but she said there's a lot of things missing compared to the IOS apps. I don't have facebook so I don't know what features are missing. She is happy to use the web version.
Preware - best thing that happened to webos in general, i think. I've done the patches but not the overclocking yet.
Flashcards lite - It is amazing how this app is helping my 6 year old son in his multiplication tables. He is now more interested to study maths probably because of the interface. This is the lite version so only one flash cards set can be installed at a time. I created some other flash cards sets online and that can be downloaded anytime and will replace the current one. Very good but quite slow, I'm not sure if this was cause by one of the installed patches.
Internalz pro - touchpad file manager, haven't had any use for it at the moment but I'm sure this will come handy when I start importing pictures, movies, etc.
Box.net app - it is a free 50G cloud storage but has a 100Mb limit and it seems that the upload speed is throttled down.
Comics HD - allows you to view your favorite comics all from one place
Mosaic Reader - rss feed reader, nice interface
I'm still waiting for a more stable version of preader native. Anyone has tried kindle yet? Does it accept epub format without much drama?
more to come once I get hold of the touchpad again.