The CrossRef Citation Plugin for WordPress reinvents the Structured Blogging plugin, but provides a minimal Lucene-based search interface to CrossRef's metadata for looking up citations, which is useful. I'd have preferred it if they'd just opened up that API and let people build their own interfaces, because the current plugin is awkward, limited and keeps timing out. The citation it returns is one long string, rather than MODS (say), so you can't use other citation styles (although I guess you could extract the pieces from the COinS string). It embeds COinS tags, but no other microformats, so is lacking compared to the Structured Blogging markup that was around two years ago.
On the other hand, the Structured Blogging plugin tried to do too much and stored the metadata in a non-standard way, so didn't really get taken up by bloggers. Maybe the combination of Zotero, a decent open CrossRef API and some plugin innovation (and aggregation along the lines of BPR3, but based on standard markup) could produce an acceptable compromise between ease of use and depth of metadata.
Update: I've added a "Blog This" box on the right-hand side of Scintilla's Conversations results page, which produces the same kind of markup as the CrossRef plugin or BPR3, ready to be copy-pasted into a blog post. Here's an example of the code it generates at the moment:
<div class="citation"> <span class="title"><a href="http://dx.doi.org/10.1371/journal.pmed.0020124" rev="review">Why Most Published Research Findings Are False</a></span>. <span class="author">John P. A. Ioannidis</span>, <span class="journal">PLoS Medicine</span>. <span class="year">2005</span>; <span class="volume">2</span>(<span class="issue">8</span>) <span class="page">e124</span> <span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Why+Most+Published+Research+Findings+Are+False&rft.jtitle=PLoS+Medicine&rft.volume=2&rft.issue=8&rft.spage=e124&rft.epage=&rft.date=2005&rft.au=John+P.+A.+Ioannidis"><!-- COinS --></span> <a href="http://scintilla.nature.com/review" rel="tag" class="review"></a> </div>