He's become so famous that's now a bit uncool to be a Fowlbot, but you simply have to read Martin Fowler to understand the state of modern software development. He's got a very balanced view of things and a talent for identifying and clearly mapping out the common problems and solutions in a field. (I'd struggle to take a senior software person seriously if they're Fowler-ignorant, or simply know better)
Rodrigo Di Olivera is a powerfully creative man, of relatively few words, who perhaps speaks loudest through the software he creates, including
Most recently, at Object Databases vendor DB4O he's released a nice piece of programming alchemy a tool that converts Java into C#.
One day I hope to port my Arcadia RPG engine to Windows Mobile (.NET Compact Framework). I expect this tool has just made that task far easier, given that Arcadia makes very few demands of its host environment's APIs.
Eric Torrebore is the driver behind Specs, the Scala BDD framework. His blog also features longer, well-written articles on programming topics that have almost always taught me something new.
Among other things, Jonas Boner comprehends and nicely explains some of the more subtle innovations in Scala relating to mixin composition and the Cake Pattern.