You can see the table and graphs for the latest Internet World Stats here.
Kalena Jordan has published a very interesting post on her blog (Ask Kalena) with tips for finding Internet Stats. She lists several of the best sources, which will save you time and trouble researching for this type of data.
Besides the sources mentioned by Kalena, I would add and recommend the Pew Internet & American Life Project. They do excellent research and publish great studies.