ProxyChecker checks a list of proxies if them are online. It also checks some hosting sites if you can download with those proxies. It can be very useful along with download managers.
Open source project that offer summary and download services on this page is a project that carry out their development work on other open source development sites. Their work is linked to this page via a feature called OFI, and their work is not carried out here on OSDN site.
