The appropriate level of dress will vary strongly depend on circumstances, so I won’t be able to say anything directly applicable to your case. But toward some of the “universal” dress codes implied upthread…
A suit is definitely not always the right choice, and a tie sometimes isn’t either. For academic positions in the sciences where research is a dominant focus of the university, dressing too business-y gives off a sense of disconnect with the culture, although this is unlikely to make or break a case. Nice slacks and nice shirt and nice sport coat is the usual combo. Visits from funding agencies, friends of the university, etc., can warrant more business-like attire, though.
I would also recommend a suit. Take a knowledgeable friend to a few thrift stores and see if you can get lucky. If you have a tailor, ask them if they have or know of any second-hand suits in your size available.
Anything you buy will likely need to be tailored to fit you, which can be pricey. Don’t skimp and have the local dry-cleaner do it - it’s worth it to pay for top rate tailoring. A good tailor makes a cheap suit look good on you.
I ALWAYS wear a suit to a job interview, and I’m in a creative field where I could get away with less. I’ve had co-workers remember the fact that I wore a suit to the interview, and I’m fine with that – it’s much better than being remembered for being too sloppy. I’m also not worried about appearing too “uptight” for a creative job, because a) other aspects of my appearance b) my personality and c) my portfolio will take care of all of that.
That said, given your situation I think your plan of a sport coat and slacks will be just fine.
Wear a suit. Every adult male should own at least one, anyway; you never know when you might have to go to a funeral or something. Dark grey or black pinstripe work for all occasions. If you’re really broke, find one at Goodwill. You can get it tailored for less than $50.
Another vote for a suit or as close to that level of formality as you can muster. Something I haven’t seen mentioned above: You’re likely to meet with administrators higher up than the department level. At my school (a private university, not a community college), all tenure-track faculty candidates have an interview with the dean.
I’m not totally convinced a suit is necessary. Sport coat, nice shirt, good slacks and shoes, a tie that you can throw on or take off as the situation merits.
How’s the search chair re: answering questions? I was in two tenure track searches. One was one day, so I wore a suit. The other was an evening and a day. I had dinner in the evening with members of the search committee and then the job talk, meetings, etc. the next. I did not know what kind of dinner it would be, so I asked the chair - she was helpful and said to dress business casual. I did, but threw a tie on as well.
It was something in the ballpark, as I got the job. Actually, both.
So I would suggest if the search chair (or the person who invited you to the interview) is approachable, to just ask. Not “dude, do I wear a suit?” but more, “It appears that the departmental dress code is pretty casual, and I don’t want to come across too stuffy. I was thinking about wearing a suit, but do you think a sport coat is more appropriate?”
If someone for some reason has a hard-on for your not wearing a suit, you’re protected, because that person suggested that you wear something else.
I honestly think that the sport coat/shirt/tie combo is more or less the uniform for academics, and in a lot of ways seems more appropriate (and in my mind, better looking and has more personality) than a Brooks Brothers suit. Even if you are meeting with the dean.
I forgot to mention that I had worked at a CC, and suits were the standard attire for those who were interviewing for (and later got) full time positions, even for support departments.
Keep us updated, and let us know what you wear to the interview!