Take a look at http://www.avalanwireless.com/product_list.htm. Click on OEM Radio Modules and check out the AW900mSPI.

The AW900m is a 900MHz digital radio with lots of range and throughput - 1.54Mbps radio channel with 900-1100kbps delivered. SPI/UART version will retail for $129 per card. These look really good - I should have a couple of modules shortly and will report on performance. The UART version is actually designated AW900mUART.