I like Fred Wilson's blog, A VC. He's a very well know venture capitalist that blogs thinking on the entrepreneur on mind.

I've no idea which are the most popular ones, but I can give you some useful info, there's a blog directory where you'll find a huge list divided into categories, so it'll make the job much easier! I guess it'll do.

You can google: "popular startups blog" and then leave it all to Google!! A huge list will display and you'll just have to check the sites. There's an awesome site, first on the search list, that includes the 50 most popular blogs. Then of course it comes the rough part, you'll have to scan all that info till you find exactly what you're looking for. Hope it helps