I recently purchased the GiGi Brazilian Hard Wax kit, and not for the bikini area. I have been suffering from dark underarms and wanted to switch to waxing to prevent any further damage from shaving.
I bought my kit off of Amazon.com for a great price. The kit came with an instructional DVD on how to Brazilian wax, Wax sticks, jar of hard wax, and a warmer with lid. It also came with a gel to place on the area before waxing, as well as a lotion for post waxing.
The only negative about waxing that I have found is that you have to let the hairs grow to a decent length in order to wax again. It can be very tempting to do a quick shave when you have a special event, but I know this will be counter productive with the lightening process.
Other things I am trying to help lighten my underarms include exfoliation, baking soda scrubs, and lemon juice. Being prego doesn't help with the hyper-pigmentation... but we will see my progress in the months to come!