Bible Study Helps

Passage and keyword search:
www.biblegateway.com - Bible Gateway
www.blueletterbible.org/index.cfm - Blue Letter Bible
http://www.biblestudytools.com/concordances/strongs-exhaustive-concordance/    - Strongs Concordance

Good source for various commentaries and sermons:
www.preceptaustin.org - Sermons/commentaries
www.pbministries.org/books/pink/pinks_archive.htm - Arthur W. Pink (Archive)
www.gracegems.org/Ryle/books.htm - J.C. Ryle
www.spurgeon.org/mainpage.htm - Charles Spurgeon (Archive)
www.monergism.com - Various resources
www.graceonlinelibrary.org  - Various articles
www.alliancenet.org  - Various articles

Commentaries:
www.biblestudyguide.org/comment/calvin/comm_index.htm - John Calvin
www.biblestudytools.com/commentaries/matthew-henry-complete - Matthew Henry