Increasing the range of cheap RF module
I used to sell modules that look like they came from the same reference design, and found they were normally good for about 100 meters but out of thousands sold here are the most common problems with range:


The SparkFun pages say lists them as being a 5V module but the datasheet says the operating voltage is up to 12V, you should definitely use that.
Those simple ASK transmitter / receiver pairs need to have a balanced signal to work well like Manchester or NRZ encoding, but the VirtualWire library you've mentioned in a comment should take care of that.
The bitrates they mention are probably somewhat optimistic, try lowering it so something like 1200bps and experiment with going even lower.
They also need a preamble for the receiver to lock on, but once again the VirtualWire  library should take care of that.
Also take a took at sending the data multiple times and additional error detection - that may help if the packets are mostly received but you get the odd inteference from being on an ISM frequency.


On the receiver side you can also look at using a larger antenna that won't have any regulatory implications. As Olin mentioned a proper ground plane for the antenna is worth looking at if practical.