Note: If this post sounds familiar, that's because it's a "rerun"--but with a lower price than when it first appeared a couple months ago.
I have an 802.11n router in my house, but not all my PCs and laptops have 802.11n adapters. Most of them run 802.11g, which drags down the overall performance of the network (it's a lowest-common-denominator kind of thing).
Cheap fix: Newegg has the Netgear RangeMax Wireless-N USB 2.0 Adapter WN111 for $9.99 shipped. It's a refurb, but, hey, something like this either works or it doesn't.
To get that discounted price (it's normally $24.99--and new units list for $70!), you need to apply coupon code EMCLVMV69 at checkout. You also need to be a subscriber to Newegg's newsletter.
As you may know, 802.11n Wi-Fi delivers dramatically faster performance and greater range than 802.11g. That's critical if you want to stream music and video (particularly HD video) around the house, and also for stuff like voice-over-IP and online gaming.
It's rare to find a USB adapter for under $20, especially without a rebate involved, so this was a no-brainer for me. (Too bad I paid $13.99 when I bought it a couple months ago!)
The adapter comes without software; you have to download the drivers and whatnot from Netgear (which is good, actually, as you'll be sure to have the latest versions of everything).
In my own little test lab, I had an 802.11n-equipped Netbook that was wreaking havoc on my network. I switched over to the WN111 and poof: problem solved. So it not only works, but works better than some built-in 802.11n adapters.
The 90-day warranty doesn't bother me, but Newegg has a no-refund policy on this product. That means you can return it for a replacement, but you can't get your money back if it doesn't work right or you don't like it. Just FYI.