I heartily recommend this blog. Its informed and very entertaining, and has a great community of contributers and bloggers.
The main man, Mark Schaefer is a terrific writer and a brilliant thinker, especially on social media! He’s the guy that wrote the tao of twitter which is in itself a fantastic book for anyone with pretensions towards social media entrepreneurial-ship! An absolute must read to get the best for your brand out of Twitter.
But the blog is really cool too, short bite sized bits of marketing thought, and the guest posters are great too. Check this one out from Social Steve
All in all some great weekend reading!