Let me share one thing that I learned these days. I'm a complete newbie in Robotics, and I'm working on a mobile robot that has a goal of traversing a stretch of rough terrain autonomously. This robot is based on a 1/8th scale RC monster truck.
I've been looking for good materials for robot base construction, and I found that PVC Expanded Foam Sheets are very good for the task. I bought a couple of 12x12 sheets from BudgetRobotics, but I also found it (I needed a bigger sheet) on my local plastic reseller.
It is reasonably priced, for example I paid $12 on a 20x30 sheet, and you have a nice color selection to choose from.
I'm doing all my designs in Corel Draw first, and then I fabricate the piece and try in the rover. My first prototype can be seen here:
Now the Colombo's egg. I found that for rapid prototyping and concept testing, it's much easier and cheaper to use foam boards. They are easily found at Target and WalMart, and you only need a scissor or a utiliy knife to cut it to shape.
Now I'm able to test a variety of shapes for my rover prior to cutting the PVC board. I bet many of you already use this technique, but I decided to share anyway.
Padu