The Forums
You can find all sorts of nuggets of wisdom on the many Starcraft 2 Forums available. There is a huge variety of information and discussion going on from all skill levels. Just be careful not to get too caught up in the ‘TheoryCraft’! ^_^
The Team Liquid forums are the biggest meeting ground for english speaking Starcraft 2 (and Starcraft 1) players on the internet. Every detail of the game has been or will be discussed on these forums at some point in time. You will also find a variety of other resources here such as live streams, links to videos and blogs, custom maps and other tools. You can also find the Official Day[9]tv Thread on the TL forums.
Find your local official Starcraft 2 forum and discuss the game with people in your region. The Battle Net forums are also a good way to find people in your region to have practice games with.
Do you know of any other good Starcraft 2 forums? If so contact me and let me know so I can put it up!