I've had some success in building traffic by using the Ping module (and more recently, the multiping module (more info here).
I have the multiping module configured to ping ping-o-matic and technorati. I've seen some new traffic coming in from those sites, but it's not growing very quickly. So, I'm trying to figure out how to get people's attention on those kinds of sites.
I also use the service_links module to provide visitors with a quick way to tell others about my sites. Not much action here, yet, but most of my sites (with the exception of exodusdev.com, which is very new) are not oriented towards technical users so I am not all that surprised.
I have also created a custom PHP block to allow users to bookmark any post on bloglines.com. You can see it in action here (look at the left sidebar for the 'Subscribe' block).
So far, it's been slow, but things are starting to accelerate.
Ok, that's enough about me, what about you?
What sites do you ping? (provide ping URLs, if possible)
What kind of results have you had?
Are there any services that have surprised you with a big response?
What strategies do you have for choosing Titles, teasers, and tags/keywords for your content, in order to ensure that it is noticed and viewed by the service's users?