
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

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

Cyberduck ftp client for mac os x
Cyberduck is number one ftp client for mac os x.
Cyberduck
FTP, SFTP, WebDAV, Cloud Files & Amazon S3 Browser for Mac OS X
homepage
direct download