A year or two back, a sweet Catholic homeschooling friend of mine told me that her boys absolutely loved their map skills books. At the time, I'd never heard of map skills. However, anything that boys like (as opposed to, say, everything else) seemed a good idea! Thus, at last year's convention I picked up Modern Curriculum Press's Maps A book. We used it this year, and it was good! We will continue this coming year with Maps B.
(Modern Curriculum Press puts out many products besides map skills, but we have no experience with their other products.)
The Maps series simply builds on basic skills - left/right, north/south/east/west, prepositions (next to, across from, etc.) to begin building the skills eventually needed for more complicated map interpretation. They're fun, easy, and not time-consuming. We completed one lesson per week (taking 10 minutes per lesson tops), and finished far before the end of the school year.
This curriculum really was an all-around winner. Inexpensive, fun, instructional, and not time-consuming. It really doesn't get much better than that.
There are many map skills books out there. Because this one has worked so well for us, I have not shopped around at all. If you'd like to browse, however, visit the Rainbow Resources booth at your local homeschool convention and check out the map skills section.
We highly recommend both the subject and this particular curriculum!