Db (The Italian based company as opposed to the top notch german company of the same name) make a small powered monitor which I use often on small gigs. Expensive but very nice, compact and versatile.
At the other end of the scale, I was at the Hitchin Folk Club last night and Kierons very smart bose rig incorporates a pair of VERY inexpensive Thoman Tbox monitors which are surprisingly good and very compact. Impressive. About £70/80 pounds each.