lftp is a sophisticated command line based file transfer program. Supported protocols include FTP, HTTP, SFTP, and FISH. It has a multithreaded design allowing you to issue and execute multiple commands simultaneously or in the background. It also features mirroring capabilities and will reconnect and continue transfers in the event of a disconnection. Also, if you quit the program while transfers are still in progress, it will switch to nohup mode and finish the transfers in the background. Additional protocols supported: FTP over HTTP proxy, HTTPS and FTP over SSL, BitTorrent protocol. IPv6 is fully supported. There are lots of tunable parameters, including rate limitation, number of connections limitation and more.
phpWebHacks is an advanced HTTP client written in PHP, a utility for HTTP scripting. It simulates a real Web browser, but you use it with lines of code rather than a mouse and keyboard. It uses pure PHP; no Curl or other fancy dependencies are needed. You can build scripts in minutes: a GMail/Yahoo/MSN contacts grabber, a YouTube video downloader, an HTTP mailer, and many more.