Recently, I was faced with an issue regarding resizing an image to a larger size. I wanted to enlarge this image to be the same size as our booth display for an upcoming conference. 
However, the only size we had available was 3×5 inches at 300dpi. Any thing poster size or larger was going to have some pixel problems.
A couple of our designers had just attended an Adobe Photoshop seminar and came back with this cool trick to enlarge an image without losing quality.
In Adobe Photoshop, go to Image, and then Image Size. If your image is not 300 dpi, go ahead and switch it without resampling. Then, with resampling on, begin bumping up the size in 10% increments. You will want to run an Unsharp Mask at every 30% or 1/3 of the process to get to the final desired image size.
Keep in mind that as you increase the size, it is compounding. So, when you repeat after the first time, 30% does not necessarily equal 3 times.
This process allowed me to take a 3×5 inch image to a 4×6 feet. I got the print back today, and the quality is amazing. I could have even gone larger with it.
