So, you're going to a conference/meetup/nerdfest and you want to do something that sets you apart from normal people. An LCD namebadge powered by an ATtiny2313 is a great way to do that. This is a general purpose LCD display unit powered by a 9V battery and a simple voltage regulator circuit (the same 7805 circuit you see absolutely everywhere). It's no-frills, but it can be etched, drilled and soldered in 1-3 hours by an experienced hobbyist, and 3-6 by a beginner/intermediate one. It all depends on how many issues you encounter along the way, and how well-equipped you are to fix them.
I found this great instructable
that shows how to breadboard this same circuit, and this is based on it.
This is my first project that I've taken from breadboard to schematic to protoboard to functioning PCB, so I'm going to try and document some of the pain I went through along the way, as well as some things that helped, in hopes that your first end-to-end electronics design is a little easier.