If you use Twitter as much as I do, then you're going to love iPhoto2Twitter, an iPhoto plugin from Blue Crowbar Software. While sending iPhone pictures to Twitter is a piece of cake, it usually takes more steps to prepare a photo on a Mac to become a photo-tweet.
The idea of iPhoto2Twitter is simple; as you're going through your iPhoto library checking out your photographic art works, you can tweet them with a few clicks. The plugin, which sells for €4.95 (approx. US$7.00), weighs in at a tiny 356 KB and works very well.
Once the plugin has been installed, tweeting photos is as easy as selecting them, choosing File > Export, and then clicking on the new iPhoto2Twitter tab. Enter your 140 characters of sparkling witticisms, choose a size for the photo, and then click Export to send the photo and tweet. I only found one issue with the plugin; as you can see, the "r" has disappeared from the name:
As a Twitter user (@stevensande) with a huge gallery of photos, I'm going to love using iPhoto2Twitter to share my images with the world, and I'm sure you will too.
Update: Within an hour of this post, Steven from Blue Crowbar had noted the missing "r" in the app (caused by a missing font on my Mac) and released version 1.1 which uses a picture instead of text for the name. That's great service from a software developer!