Polipo - A small and fast caching web proxy (a web cache, an HTTP proxy, a proxy server).

Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

ExaProxy - ExaProxy is a a high-performance non-caching proxy.

Airborn - Create and edit documents online without sacrificing your privacy

Squid Proxy - Website Content Acceleration and Distribution. Thousands of web-sites around the Internet use Squid to drastically increase their content delivery. Squid can reduce your server load and improve delivery speeds to clients.

Bit.ai - Bit is a smart real-time document collaboration platform for teams to create interactive documents, manage digital content and track document insights.