Originally Posted by Gargamel

I don't know of any off hand, but If you take it to a local print shop (kinko's etc), they should do it for you. Seeing as you have to get it printed and mounted anyways......

The problem is, the information that allows the lines to stay smooth, doesn't exist at the larger image sizes. So the programs have to extrapolate the info from the surround pixels, and that's what leads to the distortion. Photoshop could probably do it, but you'd probably be editing a lot by hand. But try it, it might work out ok. Try switching formats too, to one that doesn't compress the image as much, so it retains a lot more of the original info, that way there will be less guess work done by the app.

I'd really just take the whole board to a print shop and ask them to to make it bigger, they should do all the work for you.