You face an uphill battle, because .edu websites tend to be maintained by university employees, who have little interest and no authority to sell links. The way to get one-way inbound links from such websites is to produce truly unique and useful content and ask them for a link. If the content is truly useful and clean, you will be surprised at how many .edu webmasters will simply add a link without asking for anything in return -- I write from experience. Unfortunately, this approach will not work at all if your website sells mortgages, pills, etc. On the other hand, if you sell technical services or equipment, highly educational articles that are on-topic will get you quality links sooner or later, providing the content is truly sublime. When you approach them, remember this: you are offering a useful website to their directory -- you're not trying to collect links for SEO purposes.