The website for this thing has been gone for a while:
http://www.hurricane-eye.webs.com/legommorpg.html
And while it's still on the web archives...
http://web.archive.org/web/20140225235948/http://www.hurricane-eye.webs.com/legommorpg.html
The download links are dead. So for the sake of, uh, preserving history, I'm reuploading this thing. Hopefully if the guy who made it is still around he doesn't mind.
-> http://oresome.rockraidersunited.com/download/307 <-
If you haven't seen it before, here's his YouTube channel: https://www.youtube.com/user/masterxilo/videos
You can customize your character a bit, jump around, and kill other players with a variety of weapons, so it's at least a better game than LEGO Minifigures Online.
Oh and you can do a little modding to explore some terrain besides what's loaded by default.
That's about it, really.
Well, side note also on the subject of old fan games - LEGO Wolf3D was a thing, too: http://www.drdanick.com/legowolf3d/