I'm sick and tired of seeing people breed without good reason. A foal is NOT a souvenir. If you want to "remember your mare" take a picture and frame it. Don't breed her past her prime to the $200 stud your neighbor owns so you can "have a piece of her". If you want a piece of her, get a bracelet made out of her tail or taxidermy her for all I care. Do NOT set yourself up with a 30 year commitment to a baby that may be (read: probably will be) nothing like her.
If your mare has kicked butt in the show pen (more than just locally), has OUTSTANDING conformation (not just color) and an amazing disposition, then you could MAYBE think about breeding responsibly. Your mare being "pretty" or "sweet" or "your first horse" are not valid reasons for her to bring yet another foal into the world. Also, if you are not out of school yet, it's a mistake. Just don't do it. You do not have the time nor the means to raise a healthy foal, and even if you did you would be at the mercy of your parents whims when it comes to selling it.
To sum up my thoughts on the matter, and to provide some effort to actually change the problem at hand, I have created the following chart. Please feel free to share, so long as the watermark is not cropped out.