Scobleizer recommends a lot of apps. Recently, Robert's had somewhat of an epiphany on why he started blogging and what PR really means to him. I love his passionates v. non-passionates debate. He drives home some really great points about the influence of early adopters on advancing new technology.
His most recent recommendation, a Firefox add-on called Ubiquity, is universally useful and deserves mention. Check out the video below.
Ubiquity for Firefox from Aza Raskin on Vimeo.