Remus Lupin

From what Sam said, I think he has suggested at least the SAS members to the Crimson Company in the past, and they scoffed at the idea that muggles could be useful.

As for finding more people through these -- he brought that up himself, actually. He said that Clifford Langworth would be able to tell us the names of other former soldiers at his own camp, but he wouldn't have been able to tell us about the people at Lincoln and Harlowe.