LATEST UPDATE: March 23, 2013
All of these wireless adapters will work with Mac OS X Snow Leopard, Lion, and Mountain Lion out of the box (unless otherwise noted); they do not require any extra kexts or helper applications to function. Just install it, and forget it. Mac OS X should automatically recognize these adapters as Airport cards (which are the wireless adapters that real Macs use). All of the adapters on this list are PCI cards, so you'll have to install them on the motherboard of your Hackintosh. USB wireless adapters cannot be recognized as Airport cards.
P.S. Since Mac OS X will think that these adapters are real Airport cards, AirDrop should work automatically, so you won't have to activate AirDrop with the normal workaround.
D-Link DWA-556 ($55)
The DWA-556 is a high-end wireless adapter with a stellar reputation in the Hackintoshing community for being easy to set up. It has the standard set of WiFi features, including support for 802.11n (the fastest wireless standard) and WPA2 security. Like all of the other cards on this list, this adapter works out of the box, on Snow Leopard, Lion, and Mountain Lion.
The DWA-556 has mostly been discontinued, and costs nearly twice as much as most mainstream wireless adapters. Since it's a relatively old model, it only supports a single wireless frequency band. Being able to work on multiple bands can make your computer connect to your router a tiny bit faster, as long as your router supports multiple frequency bands as well. Most people really won't care about this, but if you're a networking enthusiast, the DWA-556's single range might be too limiting for you. Still, if you're looking for a proven way to get WiFi on your Hackintosh, the DWA-556 is a safe bet.
ASUS WL-138g V2 ($20-35)
Though it has been officially discontinued, you can still easily find units of the WL-138g V2 on sale across the internet. Compared to its higher end counterparts, it's still one of the cheapest Hackintosh-compatible adapters on the market. Admittedly, the WL-138g V2 isn't winning any races in terms of speed: the data rate of the WL-138G V2 tops off at 54 Mbps, which is far lower than the maximum speeds of the newest adapters. In addition, it doesn't support the 802.11n network standard, and can only operate on a single frequency band. But that's besides the point: none of this really matters if you just want a cheap and easy way to get WiFi working on your Hackintosh. The WL-138g V2 can do that for you.
TP-LINK TL-WDN4800 ($30-45)
recommended by tonymacx86 himself. Both Mountain Lion and Lion automatically detect this card as an Airport card; unfortunately, Snow Leopard doesn't work.
The TL-WDN4800 is pretty cheap as far as WiFi adapters go, usually priced in the $30-40 range. It supports the 802.11n standard and WPA2 security, and unlike the DWA-556, it works on three separate frequency bands. Like I said earlier, only networking enthusiasts will care about this, but it's important to keep in mind nevertheless. Overall, the TL-WDN4800 is a great choice for your Hackintosh.
Rosewill N900PCE ($25-35)
The best part about the N900PCE? It consistently underprices the TL-WDN4800 by $5-10. For that price, you get a great WiFi adapter that supports all of the frills: 802.11n, WPA2 security, three frequency bands, and so forth. While the N900PCE is not nearly as well-documented in the Hackintosh community as its better-known cousin, if you're willing to wander a bit off the beaten path, then it's an excellent (and remarkably cheap) choice for your Hackintosh.
All you need is an Apple WiFi chip, an adapter, and a small amount of hackery. Apple uses standard Broadcom WiFi chips inside their Macs, so you can easily buy one of these chips from a spare-parts seller, or on eBay. Once you have the chip, all you have to do is fit it on a PCI adapter, so that you can attach the chip to your Hackintosh's motherboard. For the full details of the process, check out this guide.
Mac OS X recognizes these self-built wireless adapters as real Airport cards-- because they are real Airport cards. These self-built adapters use real Apple WiFi chips, so technically, they're exactly the same as the Airport cards that real Macs use. Regarding performance, these WiFi chips support the 802.11n standard and WPA2 security, and they're dual-band, meaning they work on two frequency bands. When it comes down to it, self-built wireless adapters will always be the cheapest and most reliable way to get WiFi on your Hackintosh.
As of March 29, 2013, there are only five choices on this list. While there are many other adapters that can enable WiFi on your Hackintosh, those adapters usually aren't natively supported by Mac OS X. Some of those adapters require special kexts, some of them require special helper apps, and some of them will only run on certain setups. The three wireless adapters on this list are the only models I could find that have been confirmed to work with Mac OS X "natively". Take your pick-- and good luck Hackintoshing.