
I stumbled upon this tutorial yesterday and thought that some of you may be interested in this. I haven't tried this myself but it does look rather interesting. The only ND filters I own are two ND8's though I have wanted a ND400 for awhile now and probably will get one shortly. I am rather impressed with the end results of this tutorial and considering how much something like a Lee Big Stopper filter costs, it would seem that this is a viable alternative. In a way the workflow is similar to a HDR workflow involving several images but that is about where that comparison ends. I am VERY curious though and will have to try this out for myself in the days to come.
Link here
[link] 
Speaking of long exposures and filters, I have another one for you all as well. Not so much a tutorial but rather a little chart which shows exposure times and shutter speed times when using a 10 stop filter (Lee Big Stopper or B&W 110) This makes things pretty easy instead of having to do the math in your head.
Link here
[link]---John