I wish to point out that computational biology is presently synonymous with bioinformatics, however, the scientific community considers them different. Though computational biology does include bioinformatics, it doesn't mean just bioinformatics i.e bioinformatics is just a subset of computational biology which also includes reaction modeling and simulations, molecular dynamics and statistical algorithms applicable to biology. Therefore I suggest that the synonym be dissolved. I am not sure where to vote for it; so I am posting it here.
Also I want to bring to the notice of everyone that some suggested tag-synonyms are still pending. These should be resolved soon.
The definition of informatics is according to different sources:
Informatics is the science of information. As an academic field it involves the practice of information processing, and the engineering of information systems. - Wikipedia
The science of processing data for storage and retrieval; information science. - OED
This site presents different definitions (and their sources) nicely.
The terms bioinformatics and computational biology are used differently in the field of biology. In fact I have even heard people saying that they are from either of the two (especially those who work on models don't like to be called bioinformaticians).
From the related old post:
I would argue that bioinformatics and computational-biology are actually different topics but in the context in which they are used here, it is more likely to be bioinformatics. - bobthejoe
Now that the site has grown I guess we need to resolve the two subjects. For example this post by GriffinEvo can be rightfully called computational biology but not bioinformatics.
Many other topics such as quantitative neuroscience, evolutionary dynamics, biomechanics, bioengineering, molecular dynamics etc make use of computational algorithms to simulate different biological phenomena. Classifying them under informatics (which is suggestive of information storage, processing and retrieval) would, in my opinion be incorrect.
Just going terminology-wise, the journal PLoS computational biology publishes articles which fall under many of the abovementioned categories including bioinformatics but other journals of classical bioinformatics are at present mostly confined to genomics and proteomics.