CurlKit - Objective C interface for remote file systemsThis project compiles a number of client networking libraries into a re-usable framework called CurlKit for downloading and uploading files from remote servers using protocols such as HTTP, FTP and SFTP. The framework can be used directly in your own applications.
It's currently in development, and mainly includes support for SFTP connections at the moment. There's more information in the Introduction page.
There is a much better project http://code.google.com/p/curlhandle/ which is a fuller implementaton of an Objective-C interface to libcurl. I was going to make this an Objective-C libcurl framework, but decided for the meantime to focus my efforts on basic file transfer protocols first.