Have you thought about bundling up a batch of 35mm slides and having them scanned so they can live alongside your digital images? The problem is, who do you send them to?
I can give you a headstart on your research in my latest Macworld article titled, Outsource your photo scanning projects. For this piece, I sent a batch of 35mm slides, negatives, and 4x6 prints to three popular services: ScanCafe, DigMyPics, and ScanDigital. All three did a good job and were great at communication along the way. But there were some differences between them also.
As a bonus, the folks over at www.digmypics.com posted the scans they made from my test batch. At the time they did the job, they didn't know I was doing research for an article. You can take a look at the work they did here.
If you're thinking about testing one of these services, make sure you read this article.