sneumersky's solution using MSDB Roles works partially, because it does allow users to be able to run, edit or create Agent jobs without being a sysadmin, but it has limitations.

1) The groups allow the users the described rights to ALL Agent jobs. I'd prefer to be able to give users the rights to manipulate some jobs but not others. For example, they should be able to run the backup job on certain databases whenever they want before directly editing the data in them, but I'd prefer they not be able to run Agent jobs on databases they don't deal with.

2) This can be done in some instances by making the user the Owner of the job, but in some cases we have more than one user we'd like to give those rights to. I thought I could do this with an AD group, but you can't make an AD Group an object owner, nor can you give an agent job two owners.

So what we have now is a situation where the users can access the Agent jobs they need, but we have to trust them not to mess with other jobs on the same instance.