Can I use my Epson L-500V digital camera as a webcam?

If you can't just simply plug it in and use it as a web cam, is there some sort of "webcam software" I could buy/download?

I don't think so. I have a bit of experience with this as I've written some webcam software before...

(See http://www.nimisis.com/software.php if you're interested)

Digital cameras that can double as a webcam usually have the function built-in (sometimes called "USB Cam")

Webcams are fairly inexpensive though so you might want to consider that?