The only thing is that the power distribution might be a little complicated for my "robot", which is pretty much 2 modded servos and soon a ping sensor in the front, but I'll keep this in mind for later projects.
Nonsense. The power distribution system of a robot is one of the most important items! Don't neglect it!
You are likely going to need a separate power source for your servos and probably the PING sensor anyhow. Set up a larger battery as I noted: Go to a hobby shop, and they should have pigtails/splitters to allow you to split the output of a pack into two. Feed one of the outputs into the barrel jack of the Arduino. Hook the other output up to another 7805 regulator (plenty of examples on the internet as to how to do this properly - you could also look at the schematic for the Arduino) to supply power to the other servos and the PING. Alternatively, you could hook up another regulator - a 7806 - to supply 6 VDC to the servos, while the 7805 supplies the PING.
Finally - if you can find them - go for low-dropout regulators (the 78xx/79xx series are not low-dropout) if you can; there are near drop-in replacements available for the more popular 78xx series regulators, but you have to do some searching.
Good luck in your project, though - whatever method you use (if you wanted to simplify things - if the above is over your head - then use two battery packs - an R/C pack for the Arduino, and a separate 4.8-6.0 VDC 4-cell AA pack for the servos, and run the PING off the Arduino's regulator (that will likely be about all you can run off the Arduino's regulator - you don't really want to do this, but it can work).
