There is a very good collection by Stephen Mack!
- Official odoo v8 docs (included with github source code)
- Official future odoo v8 docs † (Developer tutorial/reference/api & Designer tutorial) (ReadTheDocs Format)
- Odoo v8 database scheme (Thanks go to Borut Jures for his work)
- Odoo's new v8 API guidelines (From OpenDays 2014)
- OpenERP v8 book (Community written)
- Official odoo how-to docs (Community written, odoo approved)
- Official OpenERP v7 docs
- Official OpenERP Web Developers Documentation v7
- Official OpenERP Technical Memento v0.7.4 (French Version)
- OpenERP v7 docs (Written by odoo silver partner - erpweb)