Today I launched GitHub's Markdown Rendering API compatible API.
http://gfm-kyanny.sqale.jp/ (Hosted by Sqale : )

This is a markdown rendering API service compatible with GitHub's Markdown Rendering API.
Pros
- No Rate Limit
- (almost) compatible with GitHub's Markdown Rendering API
- API endpoint path is same
- Input data format is compatible
Cons
- Does not support GitHub integration
modeparameter will be ignoredcontextparameter will be ignored
Of course this service is FREE.
See the documentation, live demo, and check the source code (MIT License).