As Draven said above, I don't know any needle or razorblade swallows where the blades don't really go in your mouth.
However, a lot of the sources you could learn from (Tomas Medina's Geek Magic is a cool DVD, though Micheal Paul's Urban Legend is great - I think that's the DVD Brian mentioned, but you can get it as an e-book currently) teach you how to treat the blades to make it abit safer. There's always the element of danger, but I think it allows for a more real performance that way
The 2 sources I mentioned above are both very good, Micheal's ebook is very comprehensive and comes with the music to do the routine to and the full script. I really think that it's one of the best ebooks I've picked up!
Geek Magic is also cool, teaches you some *ahem* interesting stuff like drinking spit... and some good stuff like razorblades, eating glass and swallowing balloons - It's also very "troma" (for those b-movie fans out there!) in it's entertainment value!
D.