In the ecosystem of the App Store, the postcard-sending app occupies a healthy niche; about two pagefuls -- 60 apps -- show up in the store, for a category weighting of 0.125 flatulans. The flatulan, of course, is the unit of measurement of App Store penetration, equaling the 480 individual apps that include the word 'fart' somewhere in their description.

Among those postcard apps, there are several standouts for virtual cards (ADA winner Postage, for example) and even a few that let you send physical postcards for a small fee (TapTapCards, goPostal and Postino).

With Postman (iTunes link/website), released today by Freeverse and Taptivate for $0.99 for iPhone OS 3.0 devices, the postcard-sending app category gets a social media boost. Postman lets you deliver your two-sided ecards (yes, the app gives you the option of simulating the back of a traditional postcard, complete with stamp graphic) via Twitter, Facebook, Tumblr, email, or simple upload to the postmanapp.com website for public review. You can already track several tweeted postcards (some which probably should never have been sent.) You can also simply save your postcards to the photo roll on the device.

Creating postcards with Postman is fast and easy; all the controls are persistent in a small icon bar at the top of the screen and large front/back and 'share' buttons at the bottom.

Postman has style and several handy features. In addition to using your own camera images/photo library or the included stock images for postcard sources, you can locate yourself on a Google map and use that graphic instead (this leverages the Map API in iPhone 3.0). Once you pick a graphic, you've got a choice of one-click filters to apply that spice up the look of your card. You can easily switch fonts and colors for your text input on the card front or back, and then send with a couple of taps.

There are a few rough edges with the first release. I found the lack of a portrait mode frustrating, as I'm actually a faster typist on the vertical keyboard; not that you'll be keying in a chapter of War and Peace, but there's quite a bit of room for copy on the postcard back and I'd like to be able to rotate on that screen. The selection widgets seem cramped a bit, particularly the one for the stock templates. It would be nice to save postcards in progress and switch back to them, but for now there's only one card and no way to revert to earlier versions.

If you want to have super-slick, email-only postcards from your iPhone, and are willing to spend a couple of dollars more for some added flexibility, you may be better off with Postage or the still-awesome Comic Touch. For $0.99, however, the first pass of Postman delivers ease of use and some very handy delivery mechanisms on the back end.