Do you own to the rights to some software ? Perhaps you are a programmer who has spent weeks & months programming & testing your own code to perfection. Perhaps you are a business who has simply acquired resell rights to a software title. Either way, you'll be wanting to distribute the software far & wide to gain some kind of reward for your efforts. 
People seek different kinds of rewards. Many, obviously, want money. Others want fame. Some just want to help out a certain part of the computing-community with a solution to a problem.
Whatever the ultimate rewards, the methods of telling the world about your software are the same. 
If your software is of the blockbuster gee-whiz variety, you can follow the approach of a book author who sends his manuscript to a publisher, or a band sending demo tapes off to record companies. 
There are big software publishers out there who will give your program a decent try-out. If they are sufficiently impressed, they will strike a deal with you - heavily weighted in their favour of course. If you are lucky you'll receive a nice royalty percentage for future sales, but in the process you'll be handing over rights & control.
Stick To What You Know
"Why not just market it myself?", you're probably thinking at this point. Well, you could, but aren't you a programmer ? Do you really want to give up coding & testing & the satisfaction of creating, in favour of doing marketing courses, organising affiliate programs, placing advertisements in all kinds of media & the 1001 other trial & error tasks that need to be done to promote a product ? There are only so many hours in the day, and if you'd rather be coding than marketing (it's a different environment, believe me), you'll want to delegate the job elsewhere. Marketing is for marketers !
So, short of handing over your software to a big publisher, there a number of ways to promote your software without devoting wads of money or changing careers from programmer to marketer. 
Free Download Sites
One such method is to contact an internet software repository, more commonly known as a download site. You probably have already used a few of them - File Pile, Jumbo, Softseek, C/Net, ZdNet, Shareware.com, .... the list goes on. What you may not realise is that there are literally hundreds more such sites out there.
For A Good Listing Visit
< http://www.windows-help.net/shareware-sites-1.html >
Not all of them have the big brand names or advertising budgets, but they each still manage to deliver tens of thousands of downloads a week to the net-surfing public.
It's certainly worth getting your own software onto these sites. Some of them will physically host your file; most will simply point to the URL that you provide.
With a little luck & editorial support from the owners of the download sites (did I hear someone say "Joint Venture"....?), you could be getting your program into the hands of hundreds of grateful computer-users within just a few weeks. If your product is shareware, many of these grateful users will soon be sending you money.