This is a pretty straightforward question so this will be one of the shorter entries this month:
- EN World - it's mainly focused on D&D type games but it ends up being the biggest tabletop RPG site and a lot of things are announced/noted/promoted there.
- Kickstarter - once you've done a few you tend to get notified of related projects, one version of the Network Effect.
- Other Blogs - I have a regular rotation of blogs I read and a lot of time they have news of a new game that I may not have seen elsewhere. If I like the blog enough to keep coming back and they think a new game looks interesting then there's a good chance I will feel the same way.
- Podcasts - similar to blogs above but also really good for things related to the game the podcast covers. Alternate rules, adventures, or a new game by the same writer or from the same company.
- Company Websites: Pinnacle, Green Ronin, Paizo, and FFG are all places I visit regularly.
That's about it!