1) Comment on their posts
2) Invite them to guest post for you
3) Interview them
4) Meet them at events
5) Email them with questions/comments
6) Invite them to an event
7) Connect with them on twitter or facebook.
8) Reply to their comments on other blogs. Find their profile page on disqus or other comment systems, and reply to their comments.
9) Write a blog post about them
10) Meet up in person