PerlShare is a DropBox drop-in to create your own private file sharing "cloud". It consists of two parts; a client and a server. The server part lets you configure a Linux machine to accept PerlShare clients. PerlShare behaves a lot like DropBox. On collisions, for example, it creates conflicted copies. The workhorse for synchronization is Unison, a very reliable piece of software from Pascal Bach.
Proximate is a social peer-to-peer (P2P) application designed for local device to device networking. It provides social communities with several user functions: Messaging, file sharing, and message boards. The application is designed to be completely P2P, i.e. servers are not needed. It only assumes TCP/IP networking, which means that it works over wireless/wired links such as ad hoc WLAN and Ethernet LAN. The application is written in Python for GNU/Linux systems with a GTK+ GUI, Nokia N900 being the primary platform.
Image Tools is a screen capture and file sharing tool. It features multi-threaded batch image resizing, conversion, cropping, flipping/rotating, watermarks, decolorizing (grayscale, negative, sepia), and optimizing. The BMP, GIF, TIFF, JPEG, PNG, and EMF image types are supported. It is compatible with MONO (only for GNOME). Multicore processing is supported to increase performance. The quality for output when optimizing is variable. Color channels can be filtered. An internal benchmarking tool is available. Indexed pixel format images can be processed.
KTorrent is a BitTorrent application that allows you to download and share files using the BitTorrent protocol. Key features include queuing of torrents, global and per-torrent speed limits, previewing of certain file types, importing of partially or fully downloaded files, file prioritization for multi-file torrents, selective downloading for multi-file torrents, kick/ban peers with an additional IP Filter dialog for list/edit purposes, UDP tracker support, support for private trackers and torrents, support for µTorrent's peer exchange, support for protocol encryption (compatible with Azureus), support for creating tracker-less torrents, support for distributed hash tables (DHT), support for UPnP to automatically forward ports on a LAN with dynamic assigned hosts, support for webseeds, scripting support via Kross, and interprocess control via DBus interface.