Here is some advice I can give you as an occasional contributor to open source projects:
Even if you don't care about what people do with your code, it's usually better to attach a license statement, first because it can identify you as the author. Since you want your code to act as sample for potential employers, I suppose that you do intend on identifying yourself as the author (I originally didn't care, and found out later that it was very important to state that I'm the author, see below). Second and more importantly, because as David Thornley points out, if you don't state your license conditions, nobody but you is legally entitled to do anything with the code but you.
This statement can be minimalist; for a project that I'd been having with a friend, we used the two-liner “Copyright 2008 TeX Users Group / You may freely use, modify and/or distribute this file.” (note that here we didn't feel necessary to state that we were the authors, but relinquished copyright to the organization we did this work for). One of our main concerns here was that if anyone was to modify our code, we wanted to hear about it in order to make the user community benefit from it.
This last point should be quite important to any programmer, I think: when I write code I'm proud of, or I feel would be useful to others, I'm always happy to know that someone has been using my code or, even better, has improved it; in that case I'm happy to modify my original code. For one particular sample I wrote once, I have witnessed how half a dozen different people used my code and adopted it slightly, without ever modifying the original code – the link above is a wiki (the code has originally been posted by someone else, but it's been mostly written by me). I found the situation very frustrating and decided from that point on that I would always state that I'm the author, and encourage people to report to me if they've found my code useful (that rarely happens, but that's another problem).
About the license you should use, other people have already explained the issue better than I would. I'd like to add two points, though:
GPL has made incompatible changes from version 2 to version 3, resulting in the odd situation that programs that have been released under GPL v2 can't be used with code distributed under v3. If you do choose GPL, I'd strongly advise the wording “GPL v2 or, at your option, any later version”. I've witnessed how one very big project was having trouble because developers contributed code under “GPL v2” which thus (probably unwillingly) prohibited its move to v3. v1 is hardly an issue, as v2 is 18 years old now. I'm not aware of any project licensed under GPL v1.
(I am not a lawyer, etc. This is based on numerous opinions I've read on mailing-lists.) If you're in the US, you're entitled to state “I, Craig Grant, hereby release this piece of code into the public domain.” In many European countries, though, this makes no legal sense: either you've been dead for over 70 years (your mileage may vary), and your work is, by law, automatically part of the public domain; or you're not, and your work can't be in the public domain. Someone (you, or people you've transferred copyright to) always hold the copyright. Which makes the need for a license statement all the more acute. I've been using my country-fellow's WTF Public License on occasion, but since you want to show your code to potential employers you may not want to refer to such wording :-)
Edit
Re your added section: of course not! The conditions you choose for distributing your work have nothing to do with the place you make it available from. It's much more the other way round: if you want to upload code to Google Code, you have to put it under some open source license. But writing open source code does not force you to upload it anywhere in particular :-)