eBay has the Worx 4.5" Worxsaw Compact Circular Saw for $40 - 20% off with coupon PSHOPEARLY (Ends 11/20 at 8AM PT; requires Paypal) = $32 with free shipping. Weights 50% less than a traditional 7.25" circular saw.
Amazon has the Dremel 11-Piece EZ Lock Cutting Kit (EZ688-01) for $14.98 with free shipping on $25+ or with Prime. List price: $28. Kit includes 4 metal-cutting wheels. 3 thin-cut wheels, 3 plastic-cutting wheels, storage box. Has excellent Amazon Reviews.
Walmart has it for the same price.