There are plenty of ways to blog a cat, and nearly all the tools out there work fine. But make no mistake: there's a blogging arms race going on.
Arguably the three most advanced contenders--slick, free Web 2.0 tools with crazy-creative feature sets--are Tumblr , Posterous  and Virb . Which one you choose depends largely on why you blog; Tumblr is a great all-purpose multimedia tool, and Virb can specialize your setup for your blog-occupation: there are setups for artists, writers, business-owners, musicians, photographers and so on. All of them incorporate other services like Twitter, Facebook and Flickr, and Tumblr has a great little iPhone app for posting on the fly. But even if you're an entrenched blogger who uses WordPress, Blogger or LiveJournal, you should check out Posterous.
Posterous is a curious tool. Its goal is to eliminate every conceivable barrier between you and your posts: no accounts, no composing posts on the Web, no desktop software, and no real technical setup required. Instead, you simply email anything you want to post to firstname.lastname@example.org, and it'll slap it up on your blogs. (Posterous knows the posts are from you, because you tell it your email addresses.)
Not only that, it can push those posts to any (or all) of the other blogs you administrate. Which posts go where depend on how you address your email; if you want something to go only to Blog A, you send the email to BlogA@posterous.com. Blog B too? Add BlogB@posterous.com to the email, and so on. Posterous would love to be your one and only, but it also seems to understand if you want to go around the block and post elsewhere, too. It's the open relationship you always wanted. From a blog.
If this has you WTFing, you're not alone. Posting on most other blogging tools isn't exactly tough -- you go to Blogger or Tumblr, or fire up software like MarsEdit, and you type your post. But there's more cognitive load involved than you realize: you enter the URL, login, grab a link, cut/paste, upload an image. Then you Tweet your post, toss it on Facebook or Friendfeed, and check it over. With Posterous, you compose one email with all the pictures, text, embed code and links you want, and the service codes it up neatly, hosts your attachments and posts it to whatever blogs and microblogs you want. Write, send, done.
The Posterous concept can be distilled even better by the company's mobile app. On Thursday it jumped aboard the iPhone bandwagon with PicPosterous , a photoblogging app. Yes, an iPhone app defeats the ultra-thin Posterous approach to blogging: it adds software into the equation, instead of asking you to compose an email. But the goal -- simplicity and speed -- is still intact. The app replaces your built-in camera app and uses Apple's in-app emailing to send your photos. Once you take a photo, it creates a post: keep on snapping and the photos and video post automatically as you shoot (and approve) them. If you email pictures to Tumblr or use its app, you're stuck snapping a picture, choosing to export, addressing an email, loading, and sending one photo at a time. PicPosterous does all that behind the scenes with no setup at all.
It's worth saying that I'm a die-hard Tumblr user who also uses Tweetie, FriendFeed, Duo for iPhone, a Drupal blog (this one), a WordPress blog and two Flickr accounts. I have them all pretty unified, but only in chunks: Tumblr takes care of Facebook and Twitter, for example, but can't talk to the Drupal blog (Posterous can). It's clear that what's driving the Posterous team -- a group of Y-Combinator  alums who raised  $725,00 last year -- isn't a fetish for email. It's a die-hard interest in unification and usability.
Posterous has other tricks up its sleeve that make it a great power-user tool, but for photo-happy bloggers, the iPhone app might be a conceptual back door that could woo non-experts. And there are a lot of photo-happy teenage bloggers. Consider the quick success of startups like DailyBooth , which calls itself the "Twitter for pictures" and has culled three million users during its incubation  (also at Y-Combi). If there are other apps that you think do mobile photo-blogging better, let us know below. If you use Posterous, let us know that, too.