Bible Study Tools

https://www.biblegateway.com/ - great for comparing translations
https://www.blueletterbible.org/ - Multiple Verse Retrieval tool is amazing, study tools

https://bible.knowing-jesus.com/ - Great for tons of cross references
http://www.tsk-online.com/ - Treasury of Scripture Knowledge online, KJV only but fast retrieval
https://www.biblestudytools.com/ - Treasury of Scripture Knowledge tool, tons of study tools
https://www.studylight.org/ - Tons of great concordances and tools
https://www.preceptaustin.org/ - bible commentaries, study tools, maps,

Quick Cross References

The fastest way is to copy them from http://www.tsk-online.com/ but that only gets you them in the KJV. One method I've come to love for getting Cross References down quickly from the Treasury of Scripture knowledge is to copy the cross references from Bible Study Tools then paste those into the Multiple Verse Retrieval tool at Blue Letter Bible, and click the most excellent "Copy to Clipboard" button. Then you go to your Sermon Prep Document and paste them in. Done. You have to do this for each list of verses for each bible verse you're getting cross references on, but this is the fastest way I've found to do it.