Shovel Knight is a great example of an indie game that went viral through the kickstarter campaign. With a preview video showing clever and fun gameplay, they were able to raise over 4x their goal and gain a large audience before the game was even finished.
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.
Desura and IndieDB were initially both operated by Desura Group, and shared a single user database. Linden Labs obtained Desura (only) in January 2014 and the sites' user bases are now split, but extensive crossover remains. Interest built through IndieDB can translate directly to sales on Desura.
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.
The Greenlight submissions with the most votes are approved in arbitrary batches, generally 50 to 100 per month. No metric is used other than raw quantity of positive votes.
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.
The contributing editors of TIGSource are free to indulge their personal gaming interests, and frequently promote titles that they feel stand out in some way.
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.
The TIGSource forums have a lively community of indie game fans and other developers with over 20,000 members. The best way to build support for your game and company is to embrace the community and hear their input.
Under the hood, itch.io is a generic file repository with no format requirements. This allows binaries for any platform to be hosted. Additional presentation options are provided for web games.
A user can upload immediately upon creating a free account, and submissions are made live immediately. Other than violations of the Acceptable Use policy, any and all content is allowed on itch.io.
Users can pay any amount they want to for a game, down to a minimum specified by the uploader. The minimum can be zero. A user can go back and pay more later if they want.
Users download installation files directly, like they would from a generic repository; there is no automated installation system, and more importantly there is no automatic update service.