arXiv.org Fulltext Search Plugin by Tom McAvoy (World-wide)

Chemistry Book Orders Search Plugin by Tom Keays (Syracuse University)

Chemistry Ejournals Search Plugin by Tom Keays (Syracuse University)

ChemRefer Plugin by Tom Keays (World-wide)

CiteSeer Search Plugin by James Riely (World-wide)

Google Books Search Plugin (World-wide)

Google Scholar Search Plugin (World-wide)

GPO Monthly Catalog Search Plugin by Tom Keays (World-wide)

WorldCat.org Search Plugin by OCLC (World-wide)

Scirus Search Plugin by Alex Plakantonakis (World-wide)

USGS Publications Search Plugin by Tom Keays (World-wide)

 

you can also reference here : http://tomkeays.com/library/plugins/