yeah.. those can really helped to increase your page rank. And i'd like to include also linking your site through forum posting using signature linking. Social bookmaking is good also with posting in blogs.
Before i forgot, directory submission also works..
Can I point out, that this is not alway the bet way of improving your page-rank. I don't have the full detail on me, but I will get it out when I get home, and post it here Sometime It will work, but you need to be careful.