By social bookmarking, image bookmarking, uploading videos on social networking sites by creating back links.

I cannot say any valuable off page activities but I can suggest you when you will go for off page work then you need to do Quality submission on it by this way you will get good promotion for your website because quality is the Key of website promotion.

Value Off page Activity Activity

Article submission
Blog Submission
Pr Submission
Local Business Listing
Social Bookmarking submission
Directory Submission
Web 2.0 Submission

Hi,
social bookmarking, forum submission, blog commenting and blog posting....
but content is very important one want to use different content for all.