The amount of books in that book store is mind-boggling.
- have a lot on one's mind
- mind is buzzing
- change (someone's) mind
- have a closed mind (about something)
- have (someone or something) on one's mind
- cross (someone's) mind
- mind goes blank
- Out of sight, out of mind.
- blow (someone's) mind
- have the presence of mind to (do something)
- last thing on (someone's) mind
- weigh on (someone's) mind
- mind over matter
- give (someone) a piece of one's mind