I want to be able to turn the valves on and off within a tenth of a second at times. Maybe I need to go with 120V valves and relays instead?

One last thing: I was looking for the resistors shown in the schematic.  I noticed that the resistor is rated 1k or 2.2k, however it appears that when I lookup resistors to purchase they come in 1k @ 1/4w, 1k @ 1w.  Some are metal film, some are carbon film..  What should I purchase? does the wattage and the film type matter?

wow, looking at the prices, I could find the 1n4004 for a penny. however I can't find the tip102.  Is there anything on the following link that could take it's place?
http://www.taydaelectronics.com/servlet/the-%28-T-%29-Transistors-cln-TIP-Series/Categories
Or do you have a suggestion of a company that sells all the pieces needed?

I am a programmer interested in interfacing a computer to the outside world, but I need a little information on the electrical side of things.  At some point  I will want to work with 50 of these solenoid valves: "http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=400190081934&ssPageName=ADME:X:eRTM:AU:1123" but at first will only connect 8 devices with the goal of being able to turn these devices on and off very fast.

1. Can I interface an Arduino to a board like this? http://denkovi.com/product/13/16-relay-board-for-your-pic-avr-project-5v.html or do I need a chip to actually talk to the board.
2. From my initial research it looks like inductive loads can be a problem, what circuitry would I need to add to the board above to handle an inductive load?  Is there a relay board that has the circuitry built in to handle deal with inductive loads?
3. At first I want to work with 5 or 6 solenoids, but as I get more comfortable with these devices I will want to scale up to around 50 or maybe even 100 relays.  Would I be able to do this on an Arduino board?  Would I be better off getting 8 channel USB boards and interfacing them to an old computer?

Brandon