Homemade Tools sent me an e-mail today with another very simple louver press made from scrap steel and it uses a scissors jack as mechanical power.
It's here ==>
https://www.youtube.com/watch?v=HG3maxBIICoYou'll still want to look at Ewhen's for the die making part ==> viewtopic.php?f=15&t=17671&hilit=louvers
There is also an example of a wooden form for making louvers by hand (i.e. hammer & dolly type stuff) on page 111 of The Book, 2nd Edition. You've got to be highly skilled or slightly masochistic to take that approach IMHO.
Way back in my build log somewhere there's a reference to louvers built as a separate insert panel. It's a "Cut & Bend" approach that produces a nice, but modern-looking louver very different from the traditional ones primarily featured in this thread. It's more like Kurt's (KB58), but slightly different. I may go that way myself. I'm too lazy tonight to search 111 pages of my log to find it, but have at it if you're interested.
Cheers,