I am strictly digital, and have my slides made by IQimaging.com. When I first started doing transfers, I didn't have a clue as to how to get my digital images into slide format in a way that was cost effective. I checked with my local service bureaus, and the cost was prohibitive (one charges $15/slide, plus setup fees). I did a web search and found IQimaging, and have been thrilled on all counts --- cost, convenience and service.
Service is extremely quick and personalized. You FTP (or email) jpgs to IQimaging, and they Fedex slides back to you. Cost varies by turnaround time, but starts as low as $2/slide, plus shipping. Quality is excellent.
I know this sounds like maybe I work for them or something, but I have no connection with the company, other than being a satisfied customer. I was so thrilled to find them, and have been so happy with their service, I think they deserve a plug. As a digital photographer who's completely addicted to the transfer process, they've made it possible for me to use my digital source art for my transfers.