Now that the Instagram API is available with last month's public beta launch, we've started to see some fun apps built on top of it. Since Instagram's only official product is an iPhone application, that means we're seeing web clients, badge widgets and even Hot-or-Not style games. The best part is that some even cross over to multiple mobile photo APIs, increasing their reach and usefulness.
Pic A Fight!: Uses the Instagram API to put photos head to head to determine the best pics. Use all public photos, or drill down by user and determine a friend's best photo. APIs: Instagram. More at our Pic A Fight! profile.
Gramfeed: Gramfeed is an Instagram web client. APIs: Google Maps, Instagram. More at our Gramfeed profile.
Snapfinch: Snapfinch provides an easy way to search for photos shared across various social photo sharing services. Currently supports searches on Instagram, Steply and Snapr. APIs: Instagram, Snapr, Steply. More at our Snapfinch profile.
BadgePlz: Social photo badges for PicPlz, Burstn, Snapr and more. Display your follower count, number of photos and photos on your website or blog. APIs: Burstn, Instagram, PicPlz, Snapr, Steply. More at our BadgePlz profile.