I've been using xrf's for a while and am totally happy with them
http://shop.ciseco.co.uk/xrf-wireless-rf-radio-uart-rs232-serial-data-module-xbee-shape-arduino-pic-etc/
I've tried nRf24l01's also very happy except for the short range, fine for home and garden.
XRF's are firmware upgradable to use the onboard uC reset pin to program arduino wirelessly