This method uses line alignment and inline-block to create a dropdown, it's 100% functional for all browsers if the dropdown links are horizontally aligned, but needs work for vertical alignment, For those who think IE6 does not support inline-block, well, it does :P
Here is a sample of what I have so far, move your mouse over the "main" link and then down.
Only Firefox, IE6-7
UPDATEStu Nicholls from cssplay.co.uk made this method work cross browser :D
This is just experimentation for fun. If you have any suggestions or tips then feel free to comment.