This project uses a BS170 (N-Channel Enhancement Mode FET) and a IRFU9120N (P-Channel HEXFET Power MOSFET) to control the DC source.
http://www.geocities.com/researchtriangle/lab/6584/dc_power_switch.html
This charger uses the nonlinear resistance of lamp filaments for controlling charge current. When the battery is low and tends to draw large currents, the lamps light up and their resistance increases, safely limiting the charge current.
http://www.electronicpeasant.com/projects/battpowr/battpowr.html
To stabilize the voltage, I used 7805 and 7812 regulators. These are easily connected and used. They also allow the external transformers to be approximately +12 - +30 volts.
http://metku.net/index.html?sect=view&n=1&path=mods/modlab/index_eng
By converting the cheap (free) ATX power supplies that can be found in any discarded computer, you can get a phenomenal lab power supply with huge current outputs, short circuit protection, and very tight voltage regulation.
http://wiki.ehow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
takes very few parts and outputs up to 10A, regulation not very good
http://www.aaroncake.net/circuits/supply2.htm
Dual Tracking Power Supply provides 0 to 15V and 0 to negative 15V.
http://members.tripod.com/michaelgellis/power3.html
http://www.musicfromouterspace.com/analogsynth/powersupply.html
This kit is a quick, neat, and inexpensive way to provide a smoothed dual unregulated DC power supply suitable for powering many audio power amplifiers.
http://www.quasarelectronics.com/3114.htm