A BSD-licensed single-header-single-source OAuth1 implementation.
If you don’t use CocoaPods, just drag and drop the two sources in and grab OMGHTTPURLRQ/OMGUserAgent. CocoaPods is easier, manages updates and manages dependencies, but is less flexible.
Usage is fully documented in the header.
Tested against Foursquare and Twitter. If you test it against something else, please fork and list the services you used it against here. Thanks.