I'm really not wanting to do my own relays and such to control AC line voltage,
is there anything prebuilt that isn't that expensive that arduino can interface with to turn on and off decent loads(120 volts 1 AMP or so)
I can do it, it's not complex but I'm wary of building my own.
Solid-state relays. SSRs.
generic OAC5 modules work great
I realize it can e done that way,
but I really want to do it to the US's electrical code.
Any plans/project links that do it up to code ?
The suggestion of using a optically coupled AC switch from gray hill sounds excellent , I just want to do it to code so I can tell my parents it's to code plus I don't have to worry.
I would suggest using X10 modules to control the 115VAC. They are UL.
You can easily interface the Arduino to the X10 transmitter in one of two ways.
Wired - http://www.arduino.cc/en/Tutorial/X10 or
Wirelessly - Arduino Playground - CM17A
You can get X10 stuff pretty cheep on ebay.
Interesing.
I'll take a look at it.
I need it to be really reliable,
one wrong move and it's hundreds of $$ in coral out the window.
Josh,
I wouldn't want to be in position to have to vouch for the reliability of X10. In fact, (full disclosure!) that is many peoples objection to it.
In my experience, unreliability comes from two main causes:
- transmitter on one phase of AC buss - receiver on the other
- receiver plugged into an outlet with a noisy device also plugged in
(#1 was solved for me with an amplifier/repeater)
It sounds like you have a lot at stake - so much so that you might want a fail safe no matter what you do. If it's temperature, perhaps you could also use the Arduino to sound an over/under temp alarm.
Just a thought.
I don't know about the US code, but I know they use SSRs inside of machinery all the time. They are by far the simplest to use, although a little pricey. If it is built into an enclosure, and properly constructed, you shouldn't have many safety concerns.
I am going to agree with the problems with X10. They are subject to noise, and I have had a few units die on me. I would not recommend these, especially if you are relying on the units for anything other room lights.
http://www.opto22.com/site/solidstaterelays.aspx
...after 30 years of service, this original "Optrol" SSR still passed all load tests for our newest SSRs...
It would be pretty tough to beat that for reliability! 
"Code" pretty much applies to permanent installation (wiring, etc) and finished devices. So using any particular device for the actual power control probably won't bring you into "code compliance." You can get assorted "power control modules", but they're aimed at the home theater and control market and are pretty expensive (http://www.smarthome.com/81301/Xantech-Controlled-AC-Outlet-AC1/p.aspx)
For more than one outlet, you can look into "remote power controllers" aimed at server rack rooms and such. (TRENDnet TK-RP08 8-Outlet Remote Power Controller - Newegg.com) (you can get them with rs232, ethenet, probably others. The insides probably involve electronics considerably more complex than an arduino, and in the end they're not much more than a solid-state (or regular) relay in a box.)
You can use an X10 or other "wireless switch" module without having to have reliable X10 over your house wiring. Typically these would use IR or radio RC to the "base unit" to control one or more outlets, BEFORE you get to the X10-over-powerline stuff that introduces "issues." You'd essentially use the arduino to "push the buttons" on the remote...
http://www.amazon.com/Northern-Tool-Equipment-RS-211-Wireless/dp/B0000ERN8H/ref=pd_cp_e_2
(A lot of these show up near the winter holidays. Wouldn't have to go outside in the weather to turn off those decorative lights.)
http://shop.christmascentral.com/Items/westinghouse%2028073?&caSKU=westinghouse%2028073&caTitle=Westinghouse%20Set%20Of%202%20In/Outdoor%20Wireless%20Remote%20Control%20Plugs
Well Hmm.
I won't spend that much since for $100 I could get what I want as a aquarium controller with the controllable outlets(no when sold separate they rip you off, $50 for one outlet)
this is more of a I have an arduino might as well put it to good use plus it has much more capacity.
Well I'll think and see what I can do,
still wary since the name, the idea of it being sold on TV and such kinda scares me some 
At $10 a piece it sounds great,
go with a three prong,
add a GFI for the whole thing and I think it could work.
Or I could go with the solid state relays at $10-$15 a pop,
and make it more tidy looking.
if I were to use relays would I just use your average perf proto board or is there something special for line voltage ?
Give them some distance from line and your low voltage,
use the same wire for your line voltage and your low voltage,
do a good soldering job and maybe pot the thing in a electrically insulating material like epoxy(after it works Lol) ?
Probably going for the remote but the idea of what I stated above makes me wary
Sorry a alarm won't work,
gotta control the lights,
skimmer, computer fans(cheapo 5V relays),
kill the lights if the tank gets too hot and maybe do a timer for them.
Quick question,
I'm about to order some parts so that the arduino will work with my fans so I don't have insane evaporation but they are on when needed.
Are reed relay switches decent for switching computer fans ?
They seem cheap and low voltage,
but I'm nimrod when it comes to some of this.
My knowledge comes from when i was 13,14 and 15,
good times, telsa coil, flyback transformer and the like.
I built a clapper circuit once that controlled 120AC using a tip120 scr with an optoisolated switch. IT works well for low current draw devices like lights but i wouldn't run a power tool off of it. "code" only describes the permanent electrical system in the house what you are worried about is safety.
just make sure that whatever you used that your connections are using thick enough wire/ traces because that is how most people start fires.