There are many dsi browser websites and here are a few i picked out:
www.dsi2play.webs.com i like this website for its many games and one of the best things is the vedio player but its chatroom is not that good.
www.dsicade.com
this is one of my favourites with its great chatroom and games but there is no profiles so that you can keep freinds lists.
www.dsibanned.webs.com
i do not like this website verymuch as it lacks in games and has a bad chatroom.

also there are many mobile sites wich you can go on like facebook, bebo and msn.

please if you know any more just comment thank you