I'm building a few sensor projects that will need to pass status messages wirelessly. The required range is standard household distances; 30 to 100 meters indoors, through walls, etc.
The XBee offerings appear to be all the rage lately, but at around $20 to $50 each, those devices would increase the project cost by one or two orders of magnitude. Conversely, the cheap no-name wireless offering reportedly have some reliability issues and are difficult to get working if you can do it at all. It would be much better to go with something with a bit more engineering behind it. Low-power would also be helpful in some of the installations, but it's not critical at the moment.
What inexpensive wireless options are there for small projects? Something that combines both the microcontroller and the wireless into a single package would also help defray costs. But again, XBee is expensive even for a microcontroller.
I haven't settled on a MCU yet; I'm considering the PIC, AVR, and MSP430 and leaning toward AVR since I typically use that for prototyping anyway; but really anything with a decent ADC and PWM will do.