The use of single sign-on and multifactor authentication for accessing the Comodo Certificate Manager is available to any subscriber that also operates an Identity Provider in the InCommon Federation. See the wiki page for details.
The InCommon Certificate Service, created by and for the higher education community, provides unlimited server and client certificates at one low fee.
The cert-users email list provides a forum for questions/answers/comments about the InCommon Certificate Service. To join, send an email to firstname.lastname@example.org with the following in the subject of the message: sub cert-users FirstName LastName. You can use the list archives (you must be a list member) to search for previously asked questions.