I've experimented with digg etc.... If you start to get a fair few diggs you'll be indexed pretty damn quick, but in my experience these have got to happen when you're on the first few pages of upcoming.

I had an article submission (with anchor text links) that got dugg a week or so ago. Within 48 hours of the submission and the start of the diggs it was indexed and the 3 targetted phrases all put my site on the 1st page of google.

There were only just over 1,000,000 competing pages, so fairly niche subject, but it shows the weight digg carries, better than any other backlink I've had to date.