Here are some to start the list...

Netflix: http://techblog.netflix.com/
Dropbox: https://tech.dropbox.com/
Twitter: https://blog.twitter.com/engineering
Facebook: https://code.facebook.com/posts/
LinkedIn: https://engineering.linkedin.com/blog
Google: http://googledevelopers.blogspot.co.uk/
Mozilla: https://hacks.mozilla.org/