I'm proud to say that OntologyOnline now hosts the Cell Cycle Ontology.
The Cell Cycle Ontology is a wonderfully rich ontology (59.000 entries), focused around cell cycle proteins, genes and interactions. A great resource if you are dealing with biochemistry, biomedicines or any other related field.
Due to it's sheer size it has been problematic to get a good look at this ontology in the past, but not anymore. The version present at OntologyOnline is the composite ontology, collecting information on four different model organisms: Arabidopsis thaliana, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Homo sapiens (us humans).
It extends to Gene Ontology (that we also host), so there is a little overlap, but if you want to jump into the fray a good place to start would be a search on Cell Cycle.
