I would recommend Scribus as well. However, I also had 2 semesters worth of being layout editor for my school newspaper, using Quark Xpress, as well as a class or two concerning layout. Both of those helped when it came time for my graduation. What I did instead of buying a bunch of graduation announcements was I created a one page pdf with scribus talking about how I was going to graduate, and then had my mom e-mail it out to all our family and family friends(she had more contacts than me). It was quite fun but could have probably used a bit more graphical refinement. I underestimated some of the difficulty in creating a nice template look from scratch. Oh well, maybe in the future.
If you're not questioning my sanity, I'm not trying hard enough