Nikon's Coolpix P1 ($550) and P2 ($400) transfer photos over Wi-Fi to computer, printer: These aren't generic Wi-Fi-equipped consumer cameras, but they do use Wi-Fi (802.11b/g flavors) as a method of transferring images as they're taken or in batch mode by date. These cameras can't upload via FTP or Web sites, or access the Internet; rather, they use Wi-Fi (ad hoc or gateway) as a way to connect remotely to a computer running its Windows or Mac OS X software. (The P1 has 8 megapixels; the P2, 5.1 MP.)
The New York Times's computer columnist David Pogue generally praises the camera and the software, but rightly beats up on Nikon for its complexity in setting up a network connection--a huge package involving a multi-step installation process with a USB cable--and the limitations they've built in. Bluetooth, frankly, would almost have been a better choice for the way that Nikon restricts Wi-Fi, except for throughput.
Pogue calls this the first wireless camera; he's right, technically, but Nikon offers a Wi-Fi adapter for their multi-thousand-dollar D2H and D2X. I wrote in passing about the D2H as part of a piece on wireless photography in May 2004 for The New York TImes. The D2H allowed Wi-Fi transmission; the D2X added remote control over Wi-Fi.
Pogue also notes that Kodak's EasyShare One is due out in another month, after several delays, but will feature a more robust Wi-Fi. The EasyShare One requires a Wi-Fi adapter like the high-end Nikon cameras--an SDIO card--but this is apparently part of the $600 cost for the 4 MP camera.
What Pogue doesn't mention, and I haven't seen noted elsewhere, is Kodak's specs for the EasyShare One state it's using 802.11b--not Wi-Fi, not 802.11g. On the other hand, my understanding of its software is that you can connect to any arbitrary Wi-Fi network, including using 802.1X at T-Mobile locations (with a later firmware upgrade), and transfer photos in a variety of ways. We'll see if that turns out to be true in the shipping version in a few weeks.