Looking at Florida public universities, UF and to a lesser extent, FSU are the most “holistic” admissions, were a significant amount of weight is even to items other than high test scores. At most of the other schools, GPA, class rigor, and Test scores dominate the admissions process, even though they do take into account other factors.
For example, at UF (based on talking with the admission folks), 50% of admissions is based on GPA/Class Rigor (most important), essay and test scores (least important). The other 50% is based on ECs, leadership, and several other factors. All other public universities, in Florida, would based more than 50% on GPA, class rigor and test scores.
Some of this information is in the Colleges “Common Data Set”. Under section “C7” (“Relative importance of each of the following academic and nonacademic factors in your first-time, first-year, degree-seeking(freshman) admissions decisions.”). Lets use UF as an example (the most “holistic”).
http://ir.aa.ufl.edu/common-data-set
Under “Nonacademic”, they list as most ("very) important; extracurricular activities, talent/ability, character/personal qualities, and volunteer work. All of these are a bit vague (welcome to holistic admissions!), but not that UF does put weight behind volunteer work.
They also list as “important”, work experience, first generation and geographical residence. UF considers it a plus if your parents have not completed college (making you the “first” generation). Ignore geographical residence for now (UF tries to admit students from across the state), as no one can tell how that will impact your admissions. UF does like to see work experience (but note that volunteer work is of more importance).
Now, lets look at Stetson University, a private university, in DeLand, Florida.
http://www.stetson.edu/administration/institutional-research/common-data-set.php
Comparing it to UF, you’ll notice that they view GPA and class rigor as most important, while everything else ranks a bit less in importance. They also rank as important, recommendations, class rank, interviews, etc. Unlike UF, they consider racial/ethic status, but not “first generation”.
Checking out the schools CDC can give you a 10,000 feet view of admissions. I would recommend vising colleges you’re interested in, talk with the admissions folks, check out the college specific forums on CC (a lot of good info can be found here), and do some research.
Good luck!
PS: Back to your original question, if I had to pick one nonacademic factor valued by colleges, other than ECs/Talent/Ability, I would pick volunteer work. But an argument could be made for interviews, recommendations, etc. It really can vary by school.