I just added this list to my latest book in the Easily Understanding Scriptures series. I thought it might be helpful to you.
Vine’s Expository Dictionary
Manners & Customs of the Bible
Dictionary & Thesaurus
Bible versions: biblegateway.com
Strong’s and lexicons: http://www.eliyah.com/lexicon.html
Strong’s and lexicons: http://www.searchgodsword.org/lex/grk
Maps and much more: http://www.ebibleteacher.com
Roman history: http://www.unrv.com/
Of course there are many more. Please share the best one you know.