IndieDB isn't just a place where you can build hype for your game: it aims to be the definitive place where you should. Everything about the site's features and interface are designed to help devs present themselves, and to kindle user interest in new games.
Your game on IndieDB has a popularity ranking, but it considers only the past 24 hours, making it only good for noticing spikes in attention. Individual pages have hit counters, which can provide a more lasting record of interest but must be tracked and compared manually.
The Concepts section of Greenlight allows incomplete projects to be put on display and receive feedback, including mock-voting as if they were full Greenlight submissions. This can be a valuable tool for refining design, presentation and marketing techniques.
In order to submit games to Greenlight at all, you must first purchase a $100 activation for your Steam account. Note that this does not represent profit for Valve: all proceeds are donated to charity. It is strictly a barrier to entry.
Spontaneous endorsements from bloggers, reviewers and other developers can generate as much or more interest as any direct effort on your part. TIGSource is positioned as a community for indie developers, making it one of the best places to catch the eye of your peers.
TIGSource Forums are designed to support a community of developers, not as an ideal marketing platform. Like most forums, you can start new topics and have limited control over the formatting of your own posts only.