Disclaimer: This may or may not improve signal strength. Testing evidence says this worked for me. Also, there's a good chance you could destroy whatever you're working on.; And with electronics, there's not much going back.
1) Cheap USB WiFi Adapter (The one I used was $3 at CompUSA)
2) External antenna adapter (I stole on off an old broken wireless router)
3) Soldering iron
What I did. (This will void any and all waranties)
For the later steps, I have images. I forgot to take "before" shots, but I have "after".
1) Pried open the USB adapter. This will vary with the exact adapter you have. Some may be clipped together, some glued. Just get a wee screwdriver and go to town, it was only $3 anyway.
2)My adapter had an obvious onboard antenna (ignore the random wire attached)
3) How to extend the range of such a crappy antenna? Solder some crap! Lucky for me I had an old wireless router that wasn't exactly working. So I opened up the router and discovered that netgear really goes all out when they build a wireless router.
4) They actually put a PCMCIA wireless pc card inside the router! I mean, the thing even still says so. For some reason I find this amusing. The red circle is where the wire that ran to the external antenna hookup was soldered to the wireless PC card. Pretty simple, heat up the connection and remove it.
5) Here is where I took a guess as to how/where to connect the external antenna wire to the USB adapter. Basically I attached it to where the onboard antenna starts.
6) I cut a little hole in the case for the wire to stick out when it's back together. And that's it! With the new adapter, you can attach any standard wireless antenna to it.
Nate Lipscy 2006