Ok, I've found online games that wirk on the DSi, If anyone wants to try them out.

1. SpaceInvasion
www.spaceinvasion.bigpoint.com is the largest Browser game I've found, with over 100,000 registered players (I think). You start off with a planet, upgrading buildings, researching technologies, building fleets, and colonizing other planets. The point is to become a top player through war and trade. Multiple universes allow you to test things in one and not ruin your best planet. In universe 2, SDKers are forming an alliance called P.D.F the Planet Defense Force. (A new name could later be a possibility). You'll have to register on a computer, though, but the game can be played on the DSi.

2. Gindis Games
www.gindis.com is a website with multiple DSi-compatible games, but the best is called Army Commander. You simply do what's mentioned in SpaceInvasion, but with modern weaponry. It's an ok game, but SpaceInvasion is probably better.

3. HullBreach Online Lite
A very simple game, you start off in a shuttlecraft and explore the sector of the galaxy shown, trading, delivering, and doing missions to make money and buy bigger ships. It's a fun way to pass the time when no one else is on, and I've been everywhere, if you need help.

4. (upcoming) The Mystical Journey.
There's a demo on the homepage. An RPG of sorts, you'll play as a boy named Jasper who travels around and must restore order in a war between the Norse Gods. Can't wait for it.

If you know of any other multiplayer(ish) browser games, leave a comment with the address and some basic info on it.

I have an account for all of these, if you want to form an alliance or need help.