CrossRef's partnership with Google is getting more press. I was a little disparaging about this last time I mentioned it, as it seemed like they were making a big deal out of a fairly simple hack, but as a search tool it does work surprisingly well.
The CrossRef link at the bottom of HubMed search results will pass your search on to a CrossRef/Google search, which is most useful when searching the sections of papers that MEDLINE doesn't index, such as Materials and Methods. It's basically a link like this:
where 'restrict=crossref' restricts the search to only those sites that are part of the CrossRef partnership (which have all opened up their fulltext archives to the Google spider), and 'filter=0' unrolls the results so that more than two pages from each site are shown.