Learning Budget - ideas wanted

Wellll howdy, I'm hoping to gather some more ideas (from those I've already read in the feed) around continuing ed, training, professional development material. 

My company offers a $2k reimbursement for this as long as it relates to developing sales/business/professional skills. Outside of the classic sales training courses, what are other types of learning you all have used that were a benefit?

For me, it can be anything: books, online courses, certifications, seminars, online material, you name it. Would appreciate content suggestions and topics/specific material you've found beneficial 

-tightlines