The essential blogs are the ones that give you insights that could only come with experience. These blogs do not teach you about silly matters like C++ syntax. They give you the ‘aha’ that can save you the trouble of experiencing these ‘aha’s first hand. Make sure you read through the archives rather than just the current article on top.The best posts are often in the archives.

Joel on Software
by Joel Spolsky

He used to be the PM for MSOffice during its hay days.
Successfully runs own company that makes bug tracking software. He is absolutely the most popular guy on the blogs.

Paul Graham

Most known for the creation of bayesian filter
Successfully runs own company. Has also turned into a venture capitalist so knows a thing or 2 about startups

The Old new Thing
by Raymond Chen

Would have sat on the top of the list had it not been specialized towards win32.
The guy’s been around in Microsoft since time immemorial.
He has created most of the shell related stuff.

Steveys Blog Rants
by Steve Yaggey

Used to be a top Yahoo programmer. Now moved to google
Make sure you read his old articles that might not be present in the blog archives. Unfortunately he doesnt produce as much as the others above.

Seth Godin

Author of many best-sellers and a renowned speaker. A business graduate from Stanford, he also ran a company which he successfully sold to Yahoo. Has cool thoughts and ideas on a range of topics.

Rands in Repose

A successfull manager in Microsoft and currently manages own company. He has also authored a popular book on Management and one of his blog articles was included by Joel in his best essays on computing book. Primarily writes about management related articles.

Coding Horror
from jeff Atwood –

He comments on an excellent range of topics including on what others have written. So it would also serve as a good notice board into whats happening too. Works for vertigo

Try to read as much of the comments as possible in these blogs. Those are valuable due to the range of opinions / stories they provide. Most riff raff would have been edited out by these superb writers anyway.

ps: If you dont know of any, i can recomment FeedReader as your tool to read the RSS feeds from blogs