Digg
Digg is a relatively new service, that's providing some real competition for sites like Slashdot and Fark.
Digg is what my Long Tail site would be if I had some cash to put into it. Users submit sites, users vote for sites (they Digg them), and the sites that get the diggs go on the front page. It's a great way to find new stuff, and unlike Fark and Slashdot, it's democratic - the users vote the stories onto the front page.
Both Fark and Slashdot have recently made minor upgrades to their code. I suspect that both sites are either starting to feel their users switching to Digg, or they're afraid it's going to happen. Fark added categories to the site so you can find just the Tech or Sports stories; Slashdot added a system for bringing more of their stories onto the front page.
I'm guessing Digg, and the disruption it represents to both Fark and Slashdot's user base, has motivated them to work on their engines, both of which are relatively stagnant compared to the rapid innovation with Digg. It's good to have some new competition in this space.