I do mostly web apps vs websites so I use:
Ventrian.com - NewsArticles a ventrian subscription is a must have and a great value
Xmod- I consider this to be the adjustable wrench of my DNN toolbox - you can built a great many things with it.
ListX/OWS - if you have at least some sql knowledge and are willing to invest some time learning it there isn't much it won't do - connect to almost any data source, internal math engine, relational apps, Google Gears, etc., etc. OWS is even easier, has a pretty cool UI, and should be releasing as an open source module most any day now.
A traffic director module is useful.
If you want a tabs module I think Tab Aggregator from dnnstuff.com is still the best. Good support too.
The core text/html module is something I use a lot for many different things. There are many plug-ins for the FCKeditor such as image editing, image maps, code highlighting, spell checking, etc.