Blades come in a wide assortment of styles, each optimized for specific tasks. Before buying, be sure to determine which one you need to use for your projects.
Circular saw blades are large, rotating blades that cut in a straight line. They're ideal for ripping large boards but less ideal for detail work. They're similar in function to cutting wheels for chop saws, but for safety you don't want to use them in chop saws, so make sure that you're using them in the right context. Band saw blades are long loops with teeth on either side. Because of their length and the looping cutting motion, they stay sharp much longer than other varieties. They work well for cutting curves and corners into woodworking projects.
Reciprocating saw blades are long, thin blades that are ideal for reaching inaccessible spots. You can get several varieties of these cutters, for cutting metal, wood or wood with nails. Jig saw blades are small and excellent for cutting into the top of a flat piece. Jigsaw and reciprocating cutters snap more often than other types, so stock up on replacements to keep on hand.
Shear blades cut through sheet metal or cables with an efficient "biting" action. They can cut exaggerated curves and corners easily. Planer and jointer blades help you file down large boards to a flat consistency, or to set joints for woodworking. They can turn undesirable boards into useful pieces.
Power tool blades reduce your overall work time and the effort you need to put into the job. You can accomplish a variety of tasks with the right model. Research your project requirements, and then grab the matching saw and blades you need to finish your job.