Alternatives to Google Scholar for citation / lit search / BibTex entries? Simple question: What alternatives are there to Google Scholar for finding citations, doing lit searches, and most importantly, downloading citation data in BibTex? 

There are lots of specialized databases (e.g. MathSciNet, ACM, etc.), but I am not aware of any that index across all disciplines the way Google Scholar does. My research is quite multidisciplinary so these specialized databases are usually insufficient.
Paid options: Scopus (bibtex export) and Web of Science (bibtex export)

Free option: Microsoft Academic Search (bibtex export).