Weeworld.com- great place for teenagers too create their own avatar talk to people make friends explore and have boyfriends/girlfriends
"Without downloading" that would require servers, nobody has done that yet, sorry.
duelingnetwork.com you can play other people around the world
playr.org
Retrouprising.com you just have to download a program called arcade ox that allows you to play the games on the website.
There is no website were you can play wwe 2011
playr.org or gbemul.com
Nup
http://snesbox.com/ you can also play Nes games on there too.
There is a website that you can use but you need Java http://gameswebfree.com/free-play-online/992/pokemon-mystery-dungeon-red-rescue-team.html
8-| Try online Flash games.
funorb.com + miniclip.com
You could try Yahoo games