Friendfeed

Friendfeed is a great way to collect together a lot of your social internet activity - it will take feeds from many sites, including YouTube, Digg, Twitter, Blogger, StumbleUpon, and son on.
You can then filter the information by using searches, and subscribe to those searches via an RSS feed. This may sound long-winded, but it's actually very quick to set up and can become very powerful - for instance you can search the whole of Friendfeed for your niche topic, and it will come up with all the Twitter comments, videos and blogs that have been created on that niche. You can obviously decide how much of this information you want to see. The great thing is that you can then keep up to date wit the latest information on your niche across all of these social sites with just a single RSS feed in something like Google Reader. Like Twitter and the other sites, Friendfeed allows you to "follow" other people to see what they're doing and what sites they recommend.
To follow me, just go here:
https://friendfeed.com/jdjenkins

- and thanks to Ed Dale for introducing me to this great resource!
Look up Thirty Day Challenge or #30DC