Here are a few SALT conferences I think are good.
Sales Tax Institute (http://www.salestaxinstitute.com) from my friend, Diane Yetter. The Institute offers live in person 3 day classes – Basics of Sales Tax and Advanced Sales Tax Workshop. These are highly rated and differ from the larger offers as they are much more intimate and provide an excellent learning opportunity. The Institute also offers monthly webinars that are not a sales pitch, but provide in depth educational content. They also have a self study online class with another coming soon.
Georgetown Advanced SALT Institute - https://www.law.georgetown.edu/continuing-legal-education/programs/cle/state-and-local-tax-institute/
Paul Hartman - http://www.hartmansaltforum.org/conference_registration
IPT has several - https://www.ipt.org/
Interstate Tax Corporation - http://www.interstatetaxcorp.com/seminars.htm
University of Milwaukee-Wisconsin SALT certificate program - https://uwm.edu/business/research/centers-institutes/deloitte-center-for-multistate-taxation/
DMA puts on several - https://www.dmainc.com/
COST and TEI have several, but only industry tax professionals are allowed to attend.
I would also look at the Big 4 firm websites (Deloitte, PwC, EY, KPMG), Grant Thornton, RSM, and BDO. They put on seminars and several webinars throughout the year. You can sign up for the e-mail list to be notified of free webinars.
What's your favorite?
If yours isn't listed above, comment or send me an e-mail at firstname.lastname@example.org.