Thread: lots of freeware

GNU Emacs: A real mans editor. Has more features than any other editor, ever.
Textpad: For people wanting better syntax highlighting and space orientation than emacs minus the 9593475389475210395 features Emacs provides.
Open Watcom: The best free and open source compiler there is. Don't dispute it, it just is, okay?
PHP Designer 2005: Maybe the best free PHP editor I've ever seen (note: I've never used Zend Studio.)
Azureus: The bittorrent client.
All the software on sysinternals.com: Written by Mark Russinovich, some of the best Windows tools on the market.
STunnel: SSL passthrough layer, you can pass everything you want through Stunnel to get an SSL encrypted session.

anything to pdf format:

http://sourceforge.net/projects/panda/

links to linux software ( some commercial apps )

http://www.linuxsoft.cz/en/
http://loll.sourceforge.net/ [ all free ]
http://www.linuxlinks.com/

then naturally:
http://freshmeat.net
savannah.gnu.org ( gnu specific sourceforge type site )

system resource monitor:

http://dindinx.net/hotbabe/
** she gets nekkid as the system uses cpu cycles **

( was linux specific, now also has windows port )

More software I have found in my... Journeys (note a lot of these I have known about for quite some time, I just forgot about them):

Code::Blocks: Pretty nice development environment.
LePutty: Sweet Windows SSH client.
OpenPERL IDE: Nice nice PERL environment. Similar to PHP Coder Pro.
PHP Coder Pro: Great PHP environment.
LispWorks: Cool environment for ANSI Common Lisp.
foobar2000: Amazing windows media player.
Snort IDS: Only one of the best open source and free IDSs available for a variety of platforms.
CScope: A freakin' sweet C tool for going through source trees. It has a variety of functions and is used by many people (specifically, auditors of source code) on a frequent basis. It can handle the source code for an entire operating system with ease.
Exuberant Ctags: Creates .tag files (which are supported by a wide variety of editors like VIM and Emacs) of a source code file, has support for a multitude of languages like Ruby, C, Perl, and Assembly, et cetera.
SVN: Absolutely marvelous source code versioning system. Many people rate it better than CVS.
Ethereal: THE network analyzer. Even used by Cisco. It auto analyzes packets for you and all that fancy jazz, although if you want to learn from the bottom-up, stay away from ethereal for a while.
NetCat: The Hackers Swiss Army Knife. Comes for NT and regular Unix variants. It can be used for a great deal of purposes, from back doors to saving an entire harddrive (my friend broke a hdd, so he inserted a livecd (german cd INSERT), made an ISO of the harddrive, and streamed it to his laptop with netcat. Not bad eh?)
NASM: Only one of the best x86 assemblers out there! Free, open source, easy to use and is quite well known among unix assembly programmers. Intel syntax is used with it.
Nmap: the absolute best port scanner out there! Don't let it fool you however, it has an extrodinary amount of features, from stealth scanning (which snort can pick up ;>) all the way to reading TCP timestamps in packets to detect uptime!
PKCrack: You know those passworded archive files? Well, if you have a copy of a file from the archive, PKCrack is the tool to break into that mofo. Providing you have a copy of a file inside the archive, PKcrack can break an archive into a decrypted form in roughtly 10 minutes or so (it took about 10 minutes for me to break one archive as a challenge, some people tried bruting the same zip and their estimated time of accomplishment was something like 4 million years.)
Digital mars C/C++ compiler: The fastest C/C++ compiler I've ever seen, it is extremely lightweight and comes in a command line form. Several tools are included. Beware however, Digital mars does not come with everything that would come with Visual C++ 7. If you want more support for libraries, you have to manually install them.
Resource Hacker: If you need to modify resources on windows (i.e. dialogs,) well, look no further.
SPIKE (fuzzer): When people need to know if their clients and servers are secure or not, they turn to the SPIKE. Free and open source, it is definately a powerful auditing tool. The magic of a fuzzer like SPIKE has to be seen before it can be believed, it's hard to really just explain it.
IRSSI: The best IRC client ever. It is only supported on linux and there are some unofficial windows builds, but it is extremely powerful and lightweight and works on almost every version of linux that has curses support. I only run windows, but I use SSH accounts just so I can use IRSSI. Yeah, I like it that much.
RadASM: Great free studio for a lot of assemblers (fasm, nasm, tasm, masm, etc. etc..)
Plone: A powerful and functional CMS written in Python. It requires the Zope framework. The easy thing about it is this: all you need is to set up Zope (you need to configure almost nothing) and then install Plone. That simple - it's installed. Highly customizable and very secure. Very recommended.
Ruby on Rails: Ruby on Rails (or RoR) is a framework written in Ruby for developing web applications with more joy and fun. And it does this well.
Any piece of software by 37signals is good if you ask me. Their whole philosophy is software is too complex, so they make more stuff, to do less, on purpose. Personally, I like it. Doesn't matter if you've never heard of them - they're still awesome.
Frostwire: basically it's exactly like Limewire, but it doesn't filter your results for things like LimeWire is starting to do.
OllyDBG: Undoubtly the best user mode debugger there is for Windows! It lacks the 'oompf' of SoftICE, and it doesn't have as many amazing disassembly features as IDA Pro, but it definately is an extremely powerful user mode debugger with a wide amount of features and some cool plugins.

OMFG ALMOST FORGOTTEN:
Tor: Tor is absolutely the best anonymity network currently available. All traffic to and fro when using Tor is theoretically 100% anonymous because of Onion Routing. Tor keeps no logs and (as much as a lot of conspiracy theorists would like to disagree) is not "one big honeypot for catching hackers." Open source, free, and works like a regular SOCKS5 proxy (which a lot of applications these days offer in their configurations, example: GAIM.) The hit in connection speed is noticable, but it is worth it if you want anonymity.

truecrypt.org -- Excellent file encryption utility, wonderful ease of use. You can mount an entire encrypted archive as a virtual disk drive and access the contained files normally.

Depends on your computer... I don't encrypt anything on my desktop, but I do encrypt some stuff on my laptop. Because my laptop is like 100 times more likely to get stolen.

I can't believe OpenVPN isn't listed!