LEDs and voltage regulation

I'm continuing to play with LEDs and electronics (see previous post on this). The idea is to build something which will accept a nominal 12V supply and regulate it to power LED light units. I've been using the LM317T regulator and experimenting with various voltages feeding the LEDs. Progress is slow because there's a lot of gardening to do at this time of year: I need it to rain so I can stay indoors and experiment more!

I'll post more on this.