Will add to this list. To nominate other RUME or RUME-related journals that have URLs, please contact me. Below are some math-education journals that while not RUME-focused may be relevant.

From: Sharon Robbert 
Organization: Trinity Christian College
Subject: Re: Where to publish "personal classroom experience" papers
To: NEXT-LIST@ENTERPRISE.MAA.ORG
Precedence: list

What about "The Teaching Professor"?
From: Stuart Boersma 
Subject: Re: Where to publish "personal classroom experience" papers
To: NEXT-LIST@ENTERPRISE.MAA.ORG
Precedence: list

Two journals come immediately to mind:

The College Mathematics Journal (MAA) publishes short "Classroom
Capsules" which may be an appropriate place.

OR

You may want to consider PRIMUS (published out of West Point I
believe).
> The *Mathematics Teacher*, an offical journal of the NCTM, is devoted to
> improving mathematics instruction in grade 8 through two-year and
> teacher-education colleges.  The publications of the NCTM present a
> variety of viewpoints....

As Judy says, it's primary focus is high-school, but it allows some
overlap with higher ed. according to the above.  In this case the author
is writing about experiences at *his* (research) institution, so his
affiliation is significant for that reason.  If he were writing about
ideas to use in teaching a high-school discrete math course, then that
would be different.

The useful suggestions I got were:

* Primus (from several people, and I should have remembered that)
       http://www.dean.usma.edu/math/pubs/primus/default.htm

* MAA's online innovative teaching exchange
        http://www.maa.org/t_and_l/exchange/exchange.html

* Teaching Professor
        http://www.magnapubs.com/newsletters/index.html#tp

* MAA's College Mathematics Journal's "Classroom Capsules" section for
  very short items.
         http://www.maa.org/pubs/cmj.html

Also: "College Teaching" publised by Heldref
http://www.heldref.org/html/body_ct.html