Your ideal schedule will depend on what you think you want to go into, and also your personal preferences. Some people want to start with something easy after step 1 and to ease their way in. Some people want to start with something terrible (like I did) and just get it out of the way. Some will insist on taking medicine first (highly overrated, medicine does NOT magically translate to the other services like you think it does).
I'll break it down a bit by specialty. This, of course, assumes that you have *some* idea of a likely specialty/specialties going in.
If you're generic and
Medicine is what you think you want to do, then ditch the conventional advice and DO NOT take it first! Try to take Pediatrics beforehand so that you get used to writing the long form H&P's and SOAPs. For the ambulatory side of medicine, it may help to have Family Medicine before IM.
If
Surgery is your interest, then congrats you're a masochist! No seriously, you will need to take two rotations before surgery: Ob/Gyn in order to learn how to scrub in (sort of) and tie knots, and medicine because the surgery shelf is so hard and has so much medicine on it.
If you like the kiddos and are thinking
Pediatrics then you should probably consider taking medicine and family medicine beforehand so that you will be somewhat familiar with both the inpatient and outpatient side of things. Peds is basically medicine for kids but without past medical history/surgical history most of the time and with some developmental/birth stuff. If you've taken IM you should at least be familiar with the format. Also, you should consider taking peds in winter since this is when the census will be the highest and you'll have the most time to shine.
If you're a man hating she-devil interested in
Obstetrics & Gynecology, then I don't know what to tell you. Just kidding!

I guess I would say take surgery beforehand to learn scrubbing in and knots and crap like that. Consider taking Family beforehand as well to get some exposure to prenatal care and well-woman/minor Gyn issues.
If you feel like a nut and
Psychiatry is your prime directive, then it probably doesn't matter as much what order you take your rotations in. Neurology might be mildly useful, and family medicine will expose you to some of the outpatient psych stuff. But psych is so different that really none of the others is like it, so just don't take it first or last.
If for some God-awful reason you want to see the incurable and
Neurology is your interest, I would say that medicine and psych would be good to have first, but medicine probably overlaps more than psych does. As long as you're familiar with hospital basics and note-writing, that's about all you can do.
If you're a jack-of-all-trades and
Family Medicine is what you think you like best, then I might consider taking it next-to-last or even last. You'll see a little of everything on this rotation, and on the shelf which is notoriously difficult! Basically the more exposure to other specialties going in the better, especially ambulatory care clerkships in peds, medicine, or OB/Gyn.
I was interested in psych and pedi going in, and I wanted to take something really bad first. Our school breaks up medicine into a fall semester block and a spring semester block so that was impossible to avoid. My schedule ended up being: OB-Psych-Medicine-FP-Neuro for fall and Peds-Medicine-Surg for spring. This gave me Jan and Feb as my peds months, which I wanted. The only thing I'd change is to have taken psych later. August and September are still pretty early on and my skills weren't great. Also OB/Gyn was pretty useless in terms of helping me prepare at all for psych. Oh another note: As someone has said if you do NOT want to do pediatrics, put it first or last. The census will be VERY low and thus it will be pretty easy. Peds is by far the most 'seasonal' of the rotations.
Good luck to the MS2's! It makes me happy to realize that soon enough someone will be coming in to take my place in the land of unending misery and torment that is third year
