Several chipmakers and manufacturers receive Wi-Fi Protected Access (WPA) certification from Wi-Fi Alliance: The first wave includes products from Atheros Communications, Broadcom, Cisco Systems, Intel, Intersil, and Symbol Technologies.
If you read Broadcom's press release, however, you can see as SmallNetBuilder points out, that there's no information about when the WPA certification firmware will roll into partner products. Microsoft has already pushed out their WPA update for XP. Apple is not mentioned in the release, nor has it revealed its plans.
Broadcom gets in a little dig at its competitors, because Broadcom's g and a/g chipsets include hardware-accelerated AES support, which is the next-generation encryption key that will be an option in 802.11i: Broadcom future proofs customers by eliminating the need for costly hardware upgrades when 802.11i is introduced. In contrast, products running software-based AES may experience severe performance degradation and will likely require new hardware or full product replacement to employ 802.11i properly.
On the flip side, I have heard that host-based AES processing won't necessary be as huge a load as anticipated. It'll shake out when companies start testing the idea: before then, there's too much variability to speculate.