ProQuest is now a provider of research databases (ProQuest Central and others), ebooks (ebrary, EBL, and MyiLibrary), discovery tools (Summon and now Primo), link resolvers (Serials Solutions and now SFX), library management system (Alma and Intota), and print books (with the recent purchase of Coutts).
EBSCO is the next largest vendor in this shrinking field. EBSCO offers research databases (EBSCOhost), ebooks (EBSCO eBooks and Audiobooks), a discovery tool (EBSCO Discovery Service), a link resolver (LinkSource), and print books (YBP Library Services). EBSCO does not offer an ILS or LMS and one has to wonder if the company will go looking to acquire one.
OCLC is the third major competitor in the library services arena. OCLC does not provide content like ProQuest and EBSCO. However, they offer a discovery tool (WorldCat) and a modern library management system (WorldShare Management Services). OCLC also offers popular services such as a proxy service (EZproxy), interlibrary loan service (ILLiad), digital collection management tool (CONTENTdm), and a virtual reference system (QuestionPoint).
If your library is looking for a comprehensive library management / discovery service / link resolver solution, you now have three vendors.
American Libraries: ProQuest to Acquire Ex Libris