AutoStitch Panorama is a $1.99 iPhone app that I bought and tried last summer. (when it was a $2.99 app). It lets you take a series of photos on your iPhone (side to side and up and down) and stitch them together to create impressive panoramic photos.
The version I first tried (3.0) was able to share panoramic photos on Facebook but not Twitter. Twitter support was just added in version 3.2.
AutoStitch Panorama 3.2 (iTunes App Store)
Language support for Chinese, Korean and Portuguese are also provided by this update. The developer (Cloudburst Research) notes that a major update will be available soon.
Panorama resulting from stitching 6 photos (2 rows of 3 photos each)