what module r u talking off?
what do u want to control with that relay?

http://dx.com/p/2-channel-temperature-sensor-relay-module-for-arduino-blue-151564?item=15

I can control small PC fan,

Are the Temperature Sensor and Relay Module separated?  how to control?

Thanks

u can plug the LM35 into the arduino sockets, too...
without any soldering...
just wrap a wire tightly around its legs and then secure it with duct tape...

the DHT would need some wires, 2...

Thanks, that is what I want to know.

do u mean this:
http://www.micropik.com/PDF/dht11.pdf ?

u need to measure humidity, 2?

this one is more accurate (regarding temperature), but unable to measure humidity:
http://www.ti.com/lit/ds/symlink/lm35.pdf

Right, I know there are DHT11 and LM35, and kind know LM35 is more accurate, but as I asked above, they are not same, DHT11 is a board, while LM35 is just a part, not sure what are the right words for them, I mean it seems LM35 is very basic and need more welding work, not something just plug or wired like DHT11.

The sensor will be with Arduino, and thinking connect Arduino to main PC by ethernet. The idea is I can have a Arduino on-site to monitor everything and feed back to main server by wire.

Also, what about LHT11 compare to LM35, I would rather do less soldering, if LHT 11 is not accurate enough, will LM35 be?

ATtiny13 is cheap, it is good if it works, could you give me more info about LM35+ATtiny13 and talks to PC?
Thanks

Thanks,  software side doesn't bother me much. I just need more info on the hardware side.

Do I just need a Arduino mother border, a ethernet shield and a DHT11? do I need do some wielding? or just wire connects?

And I heard DHT11 is not stable for temperature connection, any idea in that?

I am thinking a on-site arduino and temp sensor and connect to ethernet since I can have a cable from my hub to the place.

Thanks