These are some blogs that I keep up with and that have a wealth of information for Enterprise Messaging Admins:
Practical 365
Paul Cunningham's Exchange blog
ExchangeMaster
Andrew Higginbotham's Exchange Blog
The EXPTA {blog}
Jeff Guillet's Exchange blog
TechNet Exchange Blog
Microsoft TechNet Exchange blog
MSExchangeGuru
Ratish Nair's Exchange blog
SuperTekBoy
Gareth Gudger's Messaging blog
Jetze's Blog
Jetze Mellema's Exchange blog
EighTwOne (821)
Michel de Rooij's Messaging Blog
telnetport25
Andy Grogen's Exchange blog
Hey Scripting Guy!
Ed Wilson's PowerShell blog
Thoughtsofanidlemind
Tony Redmond's Exchange blog
Shudnow
Elan Shudnow's Exchange and Lync blog
Jeff Shertz's Blog
Jeff Shertz's Lync Blog
Ehloworld
Pat Richards' Unified Communications blog
UCKen
Ken's Unified Communications blog
Tom Talks
Tom Arbuthnot's Lync blog
PeteNetLive
Pete Long's Enterprise Messaging blog
LyncUC
Thomas Poett's Unified Communication blog
JC's Blog-O-Gibberish
John A. Cook's Lync and Exchange blog
