if you're curious to know more about developing applications using mxml, flex builder, and the flex framework, here are some free and pay resources to try:
>> Flash Programmers: Build RIAs with Flex Builder 2
Free Breeze Seminar by Phil Heinz. Bear in mind that this was produced when Flex Builder 2 was in beta 2. Still definitely useful though.
>> Adobe Flex 2 Rich Internet Applications
Paid DVD course by James Talbot, published by Total Training
($149.99, less 20% if you use this coupon code: save20flex2)