This site looks hand coded to me (from the weird looks of the source), so a good old text editor is all you need. You might be able to find some templates on-line though for free like at Open Source Web Design.
Flash would work, but remember that it won't work on all devices, and those it works on it may not work well due to memory restrictions and strange scaling. i.e. it would work on an Android phone, but probably wouldn't look right.
A few hundred lines of CSS a couple of images through Gimp and a little HTML should do it.
i would use, photoshop to create the images, slice them up, open dreamweaver and code them in. flash could be used, but as Joe said, it may not be the best option.. dont forget google can't see flash stuff...