I've now got some nRF24L01+ transceivers for sending the data.

This means the Arduino only uses about 7mA on average. Definitely going to be able to run one wireless sensor with solar panels forever with this setup.

Matt : Is this thread one of the ones with a bug making it invisible?

It was till you posted just then.

Yes, but it should correct itself as you reply to them.

Got a soldering station and solder, solder wick, and some other bits on my Christmas list.

Might add an Arduino clone starter kit too, the SainSmart UNO. Comes with all sorts of bits:

1xUNO R3, 1x1602 LCD Module, 1xUSB Cable, 1xBuzzer, 1xNixie Tube, 1xTemperature Sensor, 1x74HC595, 1xInfrared Remote Control,
1xInfrared Receiver, 1xPhotoresistor, 1xPotentiometer, 2xTilt sensor, 4xPushbuttons, 1xRGB, 1xFlame Sensor, 1xCell Box,
1xHC-SR04, 1xPrototype Shield, 1xMini Breadboard, Resistors, Jumper wires, LEDs

Got my wedge tip (bad quality, night get a decent one instead) for my soldering iron and had a quick go at desokdering and resokdering a connection. Definitely seemed easier and quicker than the pointy one.

Had a play with my Arduino last night and made a LED flash. Woo :D

Why do Americans say sodder instead of solder?

Perhaps for the same reason that you wrote "night" instead of 'might', and "desokdering and resokdering" instead of 'desoldering and resoldering'. Spill awtocorekt.

Are you drunk?

They typo when they talk?

No, unfortunately :(

You could have lied, no one would have known the truth!

You are probably correct, easy to mistake my rubbish mobile typing with drunkenness.

Looks like the tri colour LED that comes with it doesn't work :( It has red, green and "blur" colours.

I was going to edit my last post but when I tried I got a blank post without what I had already written.

If I connect one of the output pins to ground and put the ground from the Arduino to one of the colour pins on the LED module the LED lights. That doens't seem right.

I've also just realised that I was probably running the LEDs with to much current. I had connected the resistors in parallel instead of series in the circuit. Oops.

How can I get two arduinos to communicate wirelessly?

I have an idea for sommat which would need two (maybe three (or you could use more I guess)) to talk to each other. Only have 1 Arduino at the mo anyway so can get the first bit working at least.

What sort of distance? Xbees have a good reputation I think.

Probably a couple of metres. I will look at Xbees.

I've seen wireless serial RF devices or WiFi modules on eBay. Wouldn't mind which type, just need to send a signal from one to the other. Could WiFi ones connect together or would it need to go through router?

Only used Xbees for simple serial point to point stuff, I don't really know the differences between the umpteen different versions. They're meant for mesh networking so I imagine it could do it peer to peer.

Have a look at nRF24L01+ adapters. Really cheap on ebay. You can get ones with a tiny onboard antenna (99p) or slightly more expensive ones with a bigger screw-on antenna (~£3).

Edit : If you want to buy some on ebay the cheap ones come from China/HK. Also, since you want more than one search for something like "nRF24L01 -1pcs pcs" to get some good prices for multiple adapters.