Reference letters for graduate school after a couple years in the industry  How does one return to graduate school after spending a couple years in the industry? In particular, what are ways of getting good recommendations? I'm not concerned about the "adjustment" to the grad student lifestyle, but rather about the application process if the goal is a top school.
I was a CS/math major at MIT for undergrad, but wasn't really sure at the time if I wanted to go into academia, so I ended up doing more software and machine learning. For a while now, though, I've been realizing that I miss the academic life, so I've been thinking about my original goals of going to grad school in pure math or computer science theory.
So how should I go about getting letters of recommendation? It's been a while since undergrad, so letters from professors and research advisors aren't really feasible (I didn't have much interaction with them in any case), and while my work now is pretty quantitative (in machine learning), my supervisors aren't really qualified to write for me.
Does taking classes help much? I live in the Bay Area, and I know Berkeley -- and possibly Stanford? -- allows people to enroll in courses. Or should I be trying somehow to do research? I'm guessing there aren't REU-type things available for me and professors willing to take the time to talk with non-affiliated students are probably pretty hard to find, so I'm not sure how to go about this.
I've seen somewhat similar questions on MO, so hopefully this isn't too soft a question!
 A: I asked for (and got) letters from undergrad profs, as well as industry supervisors.  I let the latter know I was looking to enter a graduate program in math.  It seems to have worked -- I just successfully finished my PhD (and am going back into industry).  :)
A: It may not suit your goals, but one approach is to enroll in a masters program before entering a doctoral program.  This could help you get back into the groove of academic life,
and also give you a chance to meet new professors who could write letters for your application to a more high-powered doctoral program.  (I once advised a student who had spent quite a long time, maybe 8 years, in the software industry before returning to academia, and 
this is the route she took.  I think it served her well; because of the masters, which involved a mixture of coursework and a small thesis, she was very solidly prepared for her doctoral work, and was one of the strongest students in her cohort.)
A: I applied to grad school after five years away from academia. Before I applied, I audited a grad math course at a local (good) university. Mainly I did this to make really sure I wanted to leave my job for grad school, but I also got a good letter out of it.
Combined with some letters from undergrad profs who knew me five years ago, this was enough to get me into PhD programs at several top 25 schools.
A: I spent 5 years at a computer-aided engineering company before going to graduate school.  I had no problem asking for letters of recommendation from my former undergraduate teachers.  That, combined with a letter of intent emphasizing my industry experience and my motivation for doing study, helped me get into UC Berkeley.
You will need letters from someone who has experienced you, either as a student or employee.  If you still feel that your undergraduate school would not be a good source of recommendation (you should not feel that way), then ask those whom you work with who have had academic experience.
Tip: ask the faculty of the department you want to join how they would feel about industry- versus academic- recommendations.  If you show yourself to be a go-getter and highly self-motivated, that will go over well in the application process.
Gerhard "Ask Me About System Design" Paseman, 2010.04.12
A: I have never served on a graduate admissions committee, but my guess is that as long as you have other evidence of your mathematical ability, it's fine to have a letter of recommendation from a nonmathematician who can discuss your drive, tenacity, curiosity, and creativity even in a nonmathematical context. When my advisor discussed graduate admissions, he said, "If someone has worked for years to master archery, you have to respect that." This does not mean everyone will feel the same way, but you might be able to get at least one letter of recommendation from your current supervisor. 
See "What to look for in applicants to graduate programs?"
