Battery plugs, etc.

I will second (3rd, 4th, etc) the suggestion on PowerPoles. Very
robust, light, versatile two part hermaphroditic system. I use 15A
contacts. Currently proprietary so there are no knock offs which
makes them somewhat expensive per connection.

Safety - One reason that I like PowerPole connectors is not that they are simply polarized (nearly all connectors are) but you simply cannot make a disastrous reversed battery to battery connection as you can on some simplistic connector systems. Ask me how I know.
Polarity - There is a "standard" positive/negative orientation for power/ground that should be followed for compatibility with other ships. See http://www.wb3w.net/powerpoleinst.htm.
Crimping - This is one down side to PowerPoles as you should use a special ratcheting crimping tool that runs $30 or so. Watch for a used one on eBay. A regular crimping tool can deform the contact so it will not mate properly to the housing. But there is always soldering... ;-)
Build you own - I have a PowerPole multi-contact block at the base of my instrument panel that has all the power, communications and control wires, each using a different color to aid trouble shooting. See http://www.chicagolandglidercouncil....etterNov11.pdf. When I take the panel home for the annual winter refurb, I can hook up a battery directly to it (same connectors at each end) because I followed the "standard" polarity for the power/ground connections. The individual colored housings have a dovetail system to solidly connect one to another. Cool.

Here are some reference materials;

Crimping Instructions - http://www.wb3w.net/powerpoleinst.htm and http://www.youtube.com/watch?v=y8ODI...eature=related
ChicagoLand Glider Council newsletter article - http://www.chicagolandglidercouncil....etterNov11.pdf
Shown in use on batteries in a "Soaring" article - http://aviation.derosaweb.net/batter...ingFeb2012.pdf
Manufacturer Site - http://www.andersonpower.com/product...onnectors.html
Vendor - http://www.powerwerx.com/anderson-powerpoles/

Good luck.