Below is a list of my favourite (Windows) Freeware applications, all of them are portable or have portable versions available and will happily run from a USB drive. Please donate to the creators of any apps you find especially useful and help support OpenSource and Freeware developers where you can.
7-ZIPUseful compression tool, supports multiple formats (Zip, Rar, Tar, 7z etc.)
[
http://www.7-zip.org]
AD-AWARE SESpyware scanner and removal tool.
[
http://www.lavasoft.com/products/ad-aware_se_personal.php]
ANGRY IP SCANNERUseful network scanner, helps detect open systems and network vulnerabilities.
[
http://www.angryziber.com/ipscan]
AVG FREEFree Antivirus application from Grisoft, includes regular updates and some scheduled tasks.
[
http://free.grisoft.com]
CLAMWINOpenSource AV program, useful to have on a USB drive
[
http://www.clamwin.com]
CPUZCPU/System Information utility.
[
http://www.cpuid.com/cpuz.php]
CRAP CLEANERSystem maintainence tool, Clears c**p and useful in conjunction with other Anti-Spyware applications.
[
http://www.ccleaner.com]
DAEMON TOOLSGood Virtual CD/DVD drive tool - allows you to mount ISO images in Virtual optical drives on your system.
[
http://www.daemon-tools.cc]
DEEPBURNERPortable CD/DVD writing application.
[
http://www.deepburner.com]
DEEPRIPPERCD->MP3 Audio Ripper
[
http://www.deepburner.com]
FILEZILLADecent FTP program, Portable version available.
[
http://filezilla.sourceforge.net]
FIREFOXMy Favourite Browser...Kicks IE in the Nuts!
[
http://getfirefox.com]
FOXIT READERGood Portable PDF reader, Much more lightweight than Adobe's.
[
http://www.foxitsoftware.com/pdf/rd_intro.php]
GAIMGood OpenSource IM client, portable edition is useful to keep on a USB drive.
[
http://gaim.sourceforge.net]
GEEKTOOLS WHOISNifty SystemTray tool, useful for looking up information about who owns a website and other info.
[
http://www.geektools.com/tools.php]
GIMPExcellent OpenSource image editor - IMHO not quite as powerul as PhotoShop but it's free and Portable so a worthwhile download.
[
http://www.gimp.org]
HIJACK THISGood Anti-Spyware analysis application - Use with Caution!
[
http://merijn.org/programs.php]
LOCKNOTEEncrypted executeable notepad files, 256-bit AES encryption so commercially uncrackable (About 300 Trillion years to break on a decent spec. machine...) - Personally I use it for storing my password lists.
[
http://locknote.steganos.com]
MCAFEE STINGERFast standalone AV application, checks for infections of the most popular "In The Wild" virus's only.
[
http://vil.nai.com/vil/stinger/]
MIKELIN STARTUPGood Control Panel addition, allows you to view Startup items from multiple locations in an easy to understand interface.
[
http://www.mlin.net/StartupCPL.shtml]
NETSTUMBLERWireless Network discovery application. Offers some nifty features if you're interested in Wireless networks.
[
http://www.netstumbler.com]
NOTEPAD++Extremely powerful Notepad application. Offers advanced text editing and highlighting geared slightly towards programmers but very handy to have.
[
http://notepad-plus.sourceforge.net]
KOMPOZERBasic Web Development tool. Useful for learning HTML, very comprehensive support documentation and tutorials.
[
http://kompozer.net]
OPENOFFICEGood, OpenSource, alternative to Microsoft office, Will run from a USB drive and also supports printing to PDF files
[
http://www.openoffice.org]
OPERAAnother alternative to Firefox, probably slightly quicker but several useful Firefox extensions are not supported in Opera.
[
http://www.opera.com]
OPERATOREncrypted portable web-browser, routes all browsing traffic via a Tor network AND Privoxy servers - Useful for the paranoid...
[
http://letwist.net/operator]
PCI FILERECOVERYData recovery application. Portable (ish) and have had fairly good results recovering files with this application.
[
http://www.pcinspector.de/file_recovery/UK/welcome.htm]
POP3 CHECKERLightweight mail checker, also useful if your mailbox has been spammed for washing away the crud.
[
http://vallen.de/freeware/index.html]
PUTTY(Encrypted) Telnet and SSH client. Portable edition available.
[
http://www.chiark.greenend.org.uk/~sgtatham/putty/]
SYSINTERNALS FILEMON2KGood file monitor application, watches what running applications are doing on your system.
[
http://www.sysinternals.com]
SYSINTERNALS REGMON2KGood registry monitor application, watches what running applications are doing in your registry.
[
http://www.sysinternals.com]
SAMSPADEHandy information retrieval tool - useful for looking up information on domains and IP addresses online.
[
http://www.majorgeeks.com/Sam_Spade_d594.html]
SIWExcellent System Information tool - Will pull information on every device on your system - also has a handy password retrieval function.
[
http://www.gtopala.com]
SPACEMONGEROld version is free, gives a graphical breakdown of your harddrive useage.
[
http://www.sixty-five.cc/download/]
SPYBOT SEARCH & DESTROYAnti-spyware tool. Portable version is available.
[
http://www.safer-networking.org/en/download/index.html]
THUNDERBIRDGood fully functional alternative e-mail client - highly customiseable.
[
http://getthunderbird.com]
UTORRENTLightweight Bittorrent client, runs from a USB drive and supports protocol encryption as well as download throttling.
[
http://www.utorrent.com]
VLCGood media player, will play pretty much any media file you can throw at it without additional codecs.
[
http://www.videolan.org/vlc/]
WACKGETDownload manager, supports resuming for large downloads etc.
[
http://wackget.com]
WINLAMEAudio -> Mp3 converter.
[
http://winlame.sourceforge.net]
WINPOOCHSecurity software, a mix of Antivirus, Firewall and Anti-trojan software. Very useful but takes a little useage to understand.
[
http://sourceforge.net/projects/winpooch]
XAMPPFully fledged web-server, allows you to serve content from your machine's IP.
[
http://sourceforge.net/projects/xampp/]
Any further additions to the list are welcome
Havelock