Linux is a clone of the Unix kernel, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance. It has all the features you would expect in a modern fully-fledged Unix kernel, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and TCP/IP networking.
cdrtools (formerly cdrecord) creates home-burned CDs/DVDs with a CDR/CDRW/DVD/BluRay recorder. It works as a burn engine for several applications. It supports CD/DVD/BD recorders from many different vendors; all SCSI-3/mmc- and ATAPI/mmc-compliant drives should also work. Supported features include IDE/ATAPI, parallel port, and SCSI drives; audio CDs, data CDs, and mixed CDs; full multi-session support; CD-RWs, DVD-R/-RW, DVD+R/+RW, BD-R/BD-RE; and TAO, DAO, RAW, and human-readable error messages. cdrtools includes remote SCSI support and can access local or remote CD/DVD/BD writers.
Clam AntiVirus is an anti-virus toolkit designed especially for email scanning on mail gateways. It provides a number of utilities, including a flexible and scalable multi-threaded daemon, a commandline scanner, and a tool for automatic database updates. The core of the package is an anti-virus engine available as a shared library.
Clonezilla is a partition or disk cloning tool similar to Symantec Ghost. It saves and restores only blocks in use on the hard drive if the file system is supported. For unsupported file systems, dd is used instead. It has been used to clone a 5 GB system to 40 clients in about 10 minutes.
MPlayer is a movie and animation player that supports a wide range of codecs and file formats, including MPEG 1/2/4, DivX 3/4/5, Windows Media 7/8/9, RealAudio/Video up to 9, Quicktime 5/6, and Vivo 1/2. It has many MMX/SSE(2)/3Dnow(Ex) optimized native audio and video codecs, but allows using XAnim's and RealPlayer's binary codec plugins, and Win32 codec DLLs. It has basic VCD/DVD playback functionality, including DVD subtitles, but supports many text-based subtitle formats too. For video output, nearly every existing interface is supported. It's also able to convert any supported files to raw/divx/mpeg4 AVI (pcm/mp3 audio), and even video grabbing from V4L devices.
VLC media player is a multimedia player, framework, streamer, and encoder. It can play inputs like files, network streams, DVDs, audio CDs, Blu-Rays, capture devices, and screens. It can play most audio and video codecs and formats (MPEG 1/2/4, H264, VC-1, DivX, WMV, Vorbis, AC3, AAC, MKV, etc.), but can also be used to convert to different formats and/or send streams through the network.
Siege is a regression test and benchmark utility. It can stress test a single URL with a user defined number of simulated users, or it can read many URLs into memory and stress them simultaneously. The program reports the total number of hits recorded, bytes transferred, response time, concurrency, and return status. Siege supports HTTP/1.0 and 1.1 protocols, GET and POST directives, cookies, transaction logging, and basic authentication. Its features are configurable on a per user basis.
GroupOffice is a groupware suite that takes your office online, implementing online collaboration and CRM. It allows you to share projects, calendars, files and email online with co-workers and clients. It is easy to use and fully customizable. It also features synchronization with PDAs and Outlook.