recruiters/HR in the job search process - how do they fit?

awesome! thanks for your insight - that's pretty much what I was wondering

At least on my campus this is how it works:

Info session is organized (HR):
At the info session you'll have the chance to speak to Partners/associates/analysts/staff/etc depending on what kind of firm it is, HR will also have reps there in case you have any questions about HR stuff.

Resume/Cover letter screening is done:
Usually managers/partners are involved in this, according to what I've heard HR is not involved in this - purely a "volunteer" task to beef up the involvement of senior peeps who want to get ahead.

Interview invites are sent:
HR will send you an email thanking for your interest and inviting you to choose a time slot to interview

Interviews:
1st round usually done by people who have been in the firm for 2-5 years.
2nd round usually done by senior managers/partners

Offer is made:
USually a senior manager/partner will call you to communicate the offer ASAP. You will also get an email and a package in the mail with all the details and the legal stuff (these two done by HR)

cdnaudit is mostly right but there are differences company to company and industry to industry.

In GM and energy stuff it can vary from having no HR involved beyond dealing with them once you get an offer. Others will be all HR people until you get to R2, they will do the presentation (with alums present to answer questions), be the contact for applying, and then will do R1 interviews. Some program managers will be an MBA alum from your school, some will be an MBA from somewhere, and some will be HR...there is definitely no size fits all.

Honestly it doesnt really matter how a company does it, I have seen all the different ways work extremely well but also have seen each be very frustrating. I think its more about the company than only how they structure their recruiting. This year might not be the best example since it was very dynamic with some programs pulling out at the very last minute or even deciding between R1 and R2 to cancel internships.