Every good carpenter and hobby wood-worker needs a durable, dependable circular saw in their tool collection.  The incredible flexibility of the circular saw makes it possible for it to do an awesome diversity of projects, which makes it among the most popular tools in most wood working shops.  The flexibility to set the depth and angle of your cut opens up the door to an amazing amount of possibilities. 
There is 2 standard designsof circular saws on the market: in-line circular saws and worm-drive circular saws.  The biggest difference between them is the location of the motor, which significantly impacts the amount of torque supplied.  With a worm-drive saw, the motor is mounted parallel to the blade.  This configuration allows the motor to transfer a large amount of power to the blade, enabling it to cut through all types of substances, from wood to metal.  Generally speaking, most pro craftsmen use worm-drive saws due to the increased power and overall flexibility.  All the same, the increased torque and power also makes them a lot more dangerous than in-line saws.  For this reason, it is my opinion that worm-drive saws should only be used by pros.  Check out a lot more information about that here: 
[http://circular-saw-reviews.info/milwaukee-6370-21-metal-cutting-saw-review/ see post]

For typical hobby work, an in-line (or sidewinder) saw is a very good option.  While having less power than a worm-drive saw, most in-line saws will have no issue getting through virtually any assignment you'll be able to give it, other than huge industrial construction.  Additionally, they're just safer, lighter and generally easier to use.  Also, make sure the circular saw you buy includes an electronic brake.  This feature will cause the flow of electricity to be reversed when you release the trigger, causing the blade to stop quickly.  This is a critical and helpful safety feature. 

If flexibility is critical to you, you'll want to think about a cordless circular saw.  This will allow you to use them virtually anywhere, without needing to haul around a generator and large extension cords.  You'll find some drawbacks to cordless circular saws: they've got less torque, and you're restricted by the runtime of the battery .  It is possible to get additional battery packs to lengthen the run time, but you will need to remember to check that they they are charged, which may be bothersome.

Make sure you consider the type of work you will be carrying out before buying any power tool.  This is particularly right with circular saws.  If you switch blades on a regular basis, getting one with a quick-change option could save you a lot of time later on.  If you'd like deep cuts, you will want a saw with a blade capacity high enough to meet your expectations.  Additionally, you should definitely look at some circular saw reviews prior to making your purchase to ensure you purchase the best circular saw for your money.

Just like I wrote at the beginning, every tradesmen and DIY'er needs a strong, dependable circular saw in their tool collection.  The awesome overall flexibility of the circular saw enables it to perform an amazing variety of duties, rendering it one of the most in-demand tools around most wood-working shops.  The flexibility to adapt the depth and angle of your cut opens up the door to loads of possibilities.