It depends. "The View From Here" says on their site
Online publication includes your personal website or blog, or anyone else's website or blog, whether or not it represents itself as a publication. In other words, if it can be found with a search engine, it's published. Workshops and similar forums are, of course, exempt - we use them and love them, too which sounds a bit vague. Other places are stricter - if they can find it, it's been published.
Aside from comps ... given the recent rash of incidents in the UK (most recently
Eamonn Griffin's "On being plagiarised") I've become more wary of presenting my work in situations where mere trust is involved.