First off allow me to apologize for such a generic question. I've done some research and my choice is still unclear.
I plan to install Linux on a secondary PC for just a handful of tasks. I would like to be able to share a printer and files on this computer with my other Windows PCs.
I am a fairly advanced Windows user, so I have a fair amount of technical experience. I am hoping this install will at least help me gain some basic knowledge of the Linux OS. I would like a somewhat common distro in the event that I may need to assist a friend or colleague in the future who is also using Linux.
I think I would prefer a graphical interface, but I am open on this.

Here's a summary of my requirements:

-fairly common Linux Distro
-Share printer with windows PCs
-Share files with windows PCs (hopefully xbox & ps3 as well)
-Graphical Interface (?)
-Free

I am thinking Ubuntu may be the right choice for me, but I would love to hear suggestions. If I missed anything important, please feel free to ask and I will provide a response. Thank you!

Ubuntu (or any of the *buntus) is a great distro to get your feet wet. It's very graphical and many things are done for you automatically. Best thing is that the install CD is also a live CD so you can check that it works with your hardware before you actually install it.

wireless sharing or wired?

search your wireless hw here http://linux.about.com/gi/dynamic/of...eshootingGuide

The linux pc will be wired to the router, but some sharing will be wireless. I am downloading Ubuntu now. I think I'm going to install that and see how it goes. My printer is a Lexmark z65. I've read of people getting it to work with Ubuntu, but with some work. I am expecting a little frustration. =)
At the risk of sounding corny, I am very excited to try a new operating system...something that's not ms.

https://help.ubuntu.com/community/SettingUpSamba might start you on the pathway.