Of course the all time most popular free downloadable genealogy program is Personal Ancestral File (PAF), available from FamilySearch. But you may not know that there are other programs available online for free. Sometimes the old adage, "you get what you pay for" applies to free software, but in the case of PAF you can certainly do better, but for the time being you aren't going to go wrong.
Most of the other so-called "free" programs are really come-ons to purchase a paid version of the same program. As such these free programs usually have some limitation that prevents full use of the features or that limits the capacity of the program to so-many entries. You can try some of these programs, and it may be that the free version is all that you need or want. From my standpoint let's just say I haven't found one that I continue to use yet. If any of my readers have a suggestion for a program that might have some potential, let me know. Here is a list of some of the programs I have found:
Family Tree Builder
There are also a couple of free genealogy database programs for the Macintosh. Do a search under "free macintosh genealogy."
I have not included programs that have a "free trial period" since they will expire just about the time you decide you like the program. A free trial period program might even be the full version of the program, but from my viewpoint, two weeks or a month, even 90 days is not free in the end.
For a more extensive list, you might try this link to KindredTrails.com
One of the all time bargains in free software isn't exactly labeled as genealogy software, but these programs help in many other ways. High on my list is OpenOffice, a collaborative program that really is free. It rivals expensive commercial programs in its capabilities and features. You do need to spend a hour or so downloading the program unless you have a very fast Internet connection, but it is widely used and very popular.
If you are very technically oriented and really want to get away from commercial programs, you can even use one of the free open source code operating systems instead of Windows, such as Linux. From the Linux site, "Linux is a free Unix-type operating system originally created by Linus Torvalds with the assistance of developers around the world. Developed under the GNU General Public License , the source code for Linux is freely available to everyone."
If you want an operating system that is a little more windows-like, but still rather technical, you can also try Ubuntu. One warning, changing your operating system may make some of your software incompatible and you may lose data. Do not switch operating systems mid-stream unless you are absolutely sure you have a separate backup or are absolutely sure you know what you are doing.
Even though we don't often think about it, Google and all of its fabulous applications is also free.
Good luck, and back up your data frequently.