I wrote a article on this with a focus on wifi pen testing, it may be of help to you.
http://resources.infosecinstitute.com/wlan-penetration-test/

There may be a few maverick networks out there, but generally you will be dealing with EAP and WPA2-PSK so focus on that  and get a good GPU rig.

Cracking wep is not that useful for pen testers, as most of the companies that can afford AND want a legitimate penetration test are not using wep. WPA-      enterprise attacks are essential and so are physical attacks on routers and access points as well as a good GPU rig.

be sure to get the alfa card with the atheros chipset as atheros is the gold standard for wifi hacking it has the best compatibility with linux

this is a newer alfa card then the one vivek recommends which in my opinion is shit it can not go into master mode which is vital for EAP attacks on modern kernels but if you can't get one from a store near where you live i recommend ace hackware they sell this particular card and ship to pretty much anywhere domestically (U.S.) for 10$  and internationally for 20$ not a bad deal ether and it's run by hackers for hackers 

your welcome i hope this helps you guys get more exposure

alfa makes a newer that can use 802.11N and has an atheros chipset the advantage the atheros chipset has is that it can go into master mode for EAP attacks the problem with the rtl8187 chipset is it can not go into mastermode to be used as a soft ap on modern linux kernels (regardless of the outdated label on the box it comes in) and it also can not use 802.11N so while yes you should use a alfa card use the AWUS036NHA not the U one both work out of the box with backtrack btw however for softap with the NHA you need hostapd from this repo http://ppa.launchpad.net/hermansson-per/ppa/ubuntu karmic and the proper config file not the hostapd in the lucid/backtrack 5 repos will not work

i swear by the alfa AWUS036NHA it has an atheros chipset so it can go into monitor,master and ad hoc modes,can do packet injection and it is 802.11N compatible it is in my opinion the best wifi card for pen testing out there

in the backtrack 5 R2 repo is a tool called u3-pwn that automates the process of setting up a U3 trojaned drive

http://acehackware.com/

you guys should check out this site for hacking hardware they are a little pricey but they have top of the line equipment i bought some stuff from them and can attest to their quality and customer service i also like that they are open to product suggestions (as in new products for them to sell)

802.1X or GTFO WEP and WPA/WPA2-PSK attacks are fine if you are attacking a home or small business network but lets face it the average client that can afford a black box pen test is running WPA enterprise and possibly a WIDS so they need to cover PEAP/EAP attacks and WIDS evasion/neutralization before i will pay for this course   

if he had a problem with the signal he would not be able to tell it was open let alone know the network existed if he can identify the encryption (or lack there of) then chances are he is getting a good enough signal to pick up whole packets

thanks a lot guys i will definitely be asking a lot of questions and no i am not the kind who needs his hand held, if i don't get it right the first time i bash my head in on it till i get it :-P

Just thought i would share with the community that i now have a paid internship with the Intrepidus group in NYC

that's a good idea thanks