Hello lager562,
To get a functional laser, you will need at a minimum these parts:
-Laser diode
-Focusing module
-Driver
-Power source
-Tools and misc. items to put it all together (soldering iron, wires, ect.)
For a red laser, the long open-can diode from the LPC-815 sled is a good place to start. It's a relatively inexpensive (~$10) sled and contains a ~250mw red diode that can be extracted. To focus your laser, a
very commonly used module is the Aixiz module (~$4); You will need to extract the laser diode from the sled and press it into the Aixiz module. Alternatively, you can purchase a pre-extracted diode that has already been pressed into a module.
Next, for the driver you have a number of options to choose from. You can build your own "DDL" driver as shown in this thread:
http://laserpointerforums.com/f42/diy-homemade-laser-diode-driver-26339.html. Or you can pick a pre-built driver such as the rkcstr or flexdrive driver.
Finally, you will need a power source for your laser. This can be in the form of a plug-in AC adapter, or just a few batteries if you want portability. The voltage your power source will need to supply depends on the diode you use, and the type of driver you pick. This power source will be connected to the driver, which will then power your laser.
Additionally, if you are willing to spend more money, you can make/buy a heatsink to increase the duty cycle of the laser, and purchase a nice host to put it all in.
BTW, it might help to search the forums first before you ask any questions. There is a lot of information to be found in older threads. If after searching you can't find the answer, then you can post your question.