You can utilize any other company's 802.11b compliant NIC. You will however get better performance from using Cisco NICs. Also, if you want to utilize TKIP and MIC, you'll need Cisco NICs to take advantage of these features.
My Linksys and Orinoco work fine with a 340 AP, but the Cisco 340 NIC has a better throughput and utilize TKIP and MIC once I did a firmware and client upgrade.