curl and libcurl is a tool for transferring files using URL syntax. It supports HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP, POP3, IMAP, SMTP, RTSP, RTMP, and FILE, as well as HTTP-post, HTTP-put, cookies, FTP upload, resumed transfers, passwords, port numbers, SSL certificates, Kerberos, and proxies. It is powered by libcurl, the client-side URL transfer library. There are bindings to libcurl for about 40 languages and environments.
libssh is a C library to access SSH services from a program. It can remotely execute programs, transfer files, and serve as a secure and transparent tunnel for remote programs. Its Secure FTP implementation can play with remote files easily, without third-party programs other than libcrypto (from OpenSSL) or libgcrypt.
edtFTPnet/Compact is an FTP library for the .NET Compact Framework. It will run on all mobile devices that support the CF, including PocketPC and Windows CE. It includes support for active and passive transfer modes, SOCKS and HTTP proxies, extensive event monitoring, directory transfers, and transfer resumption. HTTP downloads are also supported.
Secure FTP Factory is a set of Java classes for communicating with FTP servers using the FTP, SFTP (FTP over SSH), and FTPS (FTP over SSL) protocols. The components offer complete FTP functionality, including the ability to transfer files, rename files, delete files, create directories, transfer directories recursively, and more.