americorp is a very respectable and well-known program. it is definitely worth doing if you have the time and you like the work. and if you do it, absolutely mention it in your app. i would go so far as to make it one of the central topics in your P.S.
Americorps is actually a blanket organization too, so there are several other programs you can get involved in under Americorps (like Teach for America), where you can actually make more money than that and get health insurance. I'm a TFA teacher in the city of Philadelphia and I have the best benefits package of any other recent college grad I know, and we get a 5k education grant (for previous loans or future schooling) for each of the two years of service. Plus, you'll get paid the normal salary for a first year teacher in whichever city you end up teaching. It's a wonderful 2-year program that I think definitely boosted my application.
There are lots of different Americorps opportunities, make sure you do one that you are interested in.
I did AmeriCorps through an organization called Community HealthCorps.
I was placed at a free clinic for the homeless in San Francisco. I was doing a lot of clinical work (medical assistant stuff) and a little bit of outreach and health education. It was a pretty insane year. The clinic was high stress and most of the patients had very high acuity needs but I loved it. If you're genuinely interested in public health and working with this population go for it. If you're just looking to pad your med school admissions resume save your time. I can't imagine doing this without having the passion for this type of work. Getting paid low wages to do something that you don't believe is not worth your time.
This has come up in all of my interviews (probably because it is my major medical work EC, not necessarily because it is Americorps) and has given me a plethora of things to talk about both in my personal statement and in general.
Thanks for the responses, seems like some good stuff!
Actually, I'm not doing any of those full-time Americorps programs. It's actually a part-time thing called Students In Services (SIS): http://www.studentsinservice.org/
It's meant for college/university students who are doing services in their communities. Americorps doesn't actually PLACE me anywhere; I go out and find my own service activities, log my hours, and report back
...so I'm not sure if it really counts, but if anyone has had experience with this or knows more about it, I'd love to hear your thoughts!