Sure...
As for Tear, see my post here - if you're familiar with desktop Linux distros, it should be easy
Other than that, here are a few suggestions:
- (Media Players) Canola or Mediabox - try both, and figure out which you like. There are a few others, such as ukmp, but those are the Big Two. If you use Youtube a lot, download MyTube, as Youtube tends to stutter in the browser. (and Vimeo? Ha!)
- Leafpad. The Notes app saves in html, and vi in the console doesn't suit everyone; a basic text editor is good. Try Geany if you want basic coding-type features
- ATI85, if you need a full-featured, "normal" calculator (it's a TI graphing calc emulator), or Free42 if you want old-skool RPN goodness (or both)
- BlueMaemo. It turns your N810 into a BT keyboard/mouse combo device - probably a good fit if you have an HTPC

Also worth mentioning is GraphicsMagick - the UI is not pretty, but it gets the job done if you need lightweight picture manipulation tools (e.g. crop/resize/transform/etc.)

Enjoy your N810, and stick around for a while