
hj-split file splitter
HJ Split is a freeware multi-platform file splitter software or a collection of it.
With HJ-Split tools you can split files into pieces and join them together on another platform.
It is usefull when you want to move a large file from one location to another.
homepage and downloads

QT ide
Qt Creator is a cross-platform integrated development environment (IDE) based on QT framework, You can develop C++ applications using QT and build it for three major operating systems and more.
home
downloads

Pencil Animaton
Pencil is an animation software which you can create classic animations in 2d like cartoons and export it as movie or flash,
With Pencil you can create flash banners or flash animations in swf format for free,
Pencil is an opensource free software for windows mac os x and linux…
homepage
downloads

Quicksilver the application launcher
Quicksilver is the application launcher you need.
I have used Namely long time but i changed to Quicksilver this month,
it has lots of features more than launching an application.
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homepage
downloads

speed crunch the calculator replacement
Speed Crunch is a very fast and high precision calculator replacement for windows mac os x and linux,
SpeedCrunch supports 50 decimal points, syntax highlighting, unlimited variables, 50 built-in functions, history, smart completion…
for more features visit homepage of SpeedCrunch or visit downloads page to download for windows, mac os x or linux

transmission bittorrent client
Transmission is a very good Bittorrent client for Mac Os X and some another Unix like systems, for example FreeBsd Solaris or Ubuntu.
Source code is also available to download.
homepage
downloads
check out Vuze if you need a bittorrent client for windows.

VirtualBox free vitualization software fox x86 computers
VirtualBox is a powerfull open source virtual machine for x86 based systems, (which you can run windows on linux or vice versa)
It runs on most Mac Os X Windows Linux Solaris and OpenBSD.
VirtualBox supports many guest operating systems, here is the list :
http://www.virtualbox.org/wiki/Guest_OSes
I have tried it installing Pardus Linux that is not listed there and it worked well, (better than qemu)
I have also tried to install Leopard (Hackintosh) on it but i could only boot and it did not run further.
homepage
downloads

wireshark, the network protocol analyzer
Wireshark is the world’s foremost network protocol analyzer.
Features
Wireshark has a rich feature set which includes the following:
- Deep inspection of hundreds of protocols, with more being added all the time
- Live capture and offline analysis
- Standard three-pane packet browser
- Multi-platform: Runs on Windows, Linux, OS X, Solaris, FreeBSD, NetBSD, and many others
- Captured network data can be browsed via a GUI, or via the TTY-mode TShark utility
- The most powerful display filters in the industry
- Rich VoIP analysis
- Read/write many different capture file formats: tcpdump (libpcap), Pcap NG, Catapult DCT2000, Cisco Secure IDS iplog, Microsoft Network Monitor, Network General Sniffer® (compressed and uncompressed), Sniffer® Pro, and NetXray®, Network Instruments Observer, NetScreen snoop, Novell LANalyzer, RADCOM WAN/LAN Analyzer, Shomiti/Finisar Surveyor, Tektronix K12xx, Visual Networks Visual UpTime, WildPackets EtherPeek/TokenPeek/AiroPeek, and many others
- Capture files compressed with gzip can be decompressed on the fly
- Live data can be read from Ethernet, IEEE 802.11, PPP/HDLC, ATM, Bluetooth, USB, Token Ring, Frame Relay, FDDI, and others (depending on your platfrom)
- Decryption support for many protocols, including IPsec, ISAKMP, Kerberos, SNMPv3, SSL/TLS, WEP, and WPA/WPA2
- Coloring rules can be applied to the packet list for quick, intuitive analysis
- Output can be exported to XML, PostScript®, CSV, or plain text
homepage
downloads page

AudaCity the free cross-platform sound editor
Audacity® is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.
homepage
download page for windows mac os x and linux/unix