At Projector Reviews, we cover not only home-theater, home-entertainment, and business/education projectors, but also mini projectors designed for packing light. One of the most popular such models on Amazon is the Vankyo Leisure 3, which measures a mere 7.8 x 5.8 x 2.7 inches and weighs in at only 2.4 pounds.
That's about the size of a small laptop, making it easy to schlep anywhere you need a projected image. The included carrying case has room for the projector, cables, and remote, and it's small enough to pack along with anything else you might need. Even better, its list price is only $99.99 with a $10 savings on Amazon as of this writing.