New old-player
Your best bet is to read the patch notes:
http://wiki.guildwars2.com/wiki/Game_updates
There have been a lot of changes sense release, read the forums for specific areas WvW, PvP, events, characters, etc. and check out some of the 3rd party GW2 websites.
TP buy/sell
http://www.guildwarstrade.com/
Event guides
http://dulfy.net/category/gw2/
Guides
http://www.gw2wiz.com/