Watch the The Bossa online guitar lesson by David Hamburger from Blues Architect

The essence of playing over chord changes isn't that complicated, it's just that the whole concept tends to get associated with playing jazz, which itself tends to be associated with playing tunes with too many chords at too fast a tempo. But blues and country players of all stripes play the changes too, often over just a few chords at a moderate tempo. For more ideas on the subject (in a major key), try this online lesson on swing soloing: http://www.acousticguitar.com/lessons/swing_soloing/1.shtml