http://www.supermariobrosonline.co.cc/ or
http://www.smf4free.com/forums/supermariobrosonline/Why don't you give this a whirl? It has:
-Over 80 playable maps
-Daily Event
-Favors (Quests)
-Fully functional friends list
-Steal the Shroom (fully functional Capture the Flag script with teams, waiting rooms, points, etc.)
-Whack-A-Monty (fully functional single-player Whack-A-Mole-like game)
-Fully functional, advanced Ammo system (reloading, different ammo types, etc.)
-Enhanced Trading System
-Easy personal messaging system
-? Blocks (you can hit them!)
-Respawn points
-Randomized damage
-Unique level up system
-Smooth character movement
-Enhanced NPC Talk System
-Working party system
-Automated Group system
-And much more!
Currently in: Beta version 1.1
I will also keep you updated on the list of additional things, in spoiler tags, if necessary.