SolarPanels:
do a bing with keywords 'Laser' and 'etalon' -- lots of info
From what I can see:
...an "etalon" is -not- anything that will help sbright33 do what he wants to do - which is to steer a beam (since he is asking about galvos and such).
shooter:
too get fast you need low mass, i would start with a speaker and glue some foil on top of it
Foil is not your best option here (won't reflect well enough). The low cost option would be to use a piece of thin acrylic mirror, or try to get a small thin piece of first-surface mirror (perhaps out of an old laser printer). Mount that to a cone...
Sometimes on ebay you'll also see people occasionally (getting more and more rare as the years go by) selling x/y steering units from old laser-disc players; these were also open-loop control (well - open-loop to extent; as-is they are open-loop, but in a laser-disc player, the system would close the servo-loop by using the tracks on the laser-disc surface and special control circuitry to keep the beam aligned properly).
Ultimately, though, for precise steering of the beam, you are going to need a feedback mechanism. That is what a laser galvo is - it's a low-mass, high-speed limited rotation servo motor capable of positioning a small bit of mirror precisely, quickly, and at the same commanded angle every time.
Common galvos typically use extremely low-mass rotors (air core) to keep overshoot/undershoot/ringing to a bare minimum, and will use capacitance or optical methods for the feedback system. It would be extremely difficult (but not impossible - as has already been linked) to build your own galvos. Using a stepper motor is not advised because the mass of the rotor will likely be too high.
What might be possible (stressing "might") would be to use a coreless motor of some type; for example, if you could find a coreless "in-runner" BLDC hobby motor, then somehow set thing up to gain feedback from the system (maybe energize one or two of the coils with a custom driver, and monitor the back EMF from the remaining coil(s) for position information?) - that might just be a doable and cheap method to make your own galvo (without needing all of the minute custom machining that seems needed for most custom galvo systems). I'll have to think on this option further...
Or - if you could somehow use a coreless servo motor, and change the gear and feedback system on it to something closer to a regular galvo - that might be possible as well. The capacitance method is actually fairly simple to do, as it just uses a couple of half-plates (one stationary, one connected to the shaft of the rotor), seperated by a small air-gap - and they form an air-gap capacitor (not unlike the variable tuning caps in old radios) as the plates turn to increase or decrease the capacitance.
Optical methods use a means of reflecting IR light (or passing it through polarized filters) onto a photo-transistor, photo-diode, etc, and measuring the amount of voltage generated or current let through.
One idea I've toyed with in my head (but never tried - I've been told it isn't practical) would be to take a small mirror, and mount it to a piezo-disc transducer; again, it would be "open-loop", but maybe it could be made to move by a small amount (maybe too small to even use the shift?). Another option would be to use - instead of large speakers - small headphone speakers (and very small, low-mass mirror pieces).