This is a place to capture other formats efforts that may or may not have any particular applicability to microformats.
The following attempts at structured data in HTML have either been abandoned, obsoleted, or discontinued by their creators.
Nonetheless they may be worthy of research and understanding, what motivated their creation, and perhaps why they failed.
- 2005-05-20...2009(?): StructuredBlogging
- 2005-11-15...2011: Google Base schema
- 2007...2011(?): Google Data API/Elements
- 2009...2009(?): Yahoo et al CommonTag.org
- 2009-05-12...2011(?): Google rdf.data-vocabulary.org
- 2010-present Facebook OGP meta tags 
- 2011-present Google/MS/Y! schema.org
- 2012-present Twitter Cards meta tags 
- 2012-present OpenMetadata.org 
We can also view each of the past and current alternatives as feedback, whether intended or not, and opportunities to improve microformats. Open source teaches us that great ideas come from everywhere, thus we should analyze and document other efforts, seeking to answer the above questions.
Research (on a separate page) the alternatives to at least answer the following questions (per microformats.org blogpost)
- What problems were these created to solve?
- Are they solving similar, overlapping, or different problems than microformats?
- If these alternative efforts are solving the same or similar problems as microformats, how can we improve microformats to meet their needs with established open standards?
- If they’re addressing different problems, are those problems that microformats should be expanded to solve?
- Did their creators know about microformats?
- Did they try using microformats?
- Are they open efforts (or at least trying to be open), or are they vendor-specific?
- If they’re open efforts, how can we best collaborate and produce even better solutions together?