I've assembled some pictures, explaining what sort of tools are out there. There are probably more tools than I've managed to assemble, but you will reach far equipped with the ones pictured here.
First, you need knitting needles. The picture above displays double-pointed needles in wood (2) and plastic (5). These usually come in fives, and are often used for knitting small circular knits, such as socks and sleeves. They come in a large variety of sizes, ranging from the smallest size 2mm/U.S. 0 (actually, I've seen 1.5 mm as well) to the largest sizes, like 12mm/U.S.17. I've seen as large as 20 mm as well.
Number (4) displays needle protectors, which are put on the tip of the double-pointed knitting needle, preventing stitches slipping of the needle. Number (3) displays crochet hooks, used when crocheting. Number (1) displays cable knitting needles, typically used in aran knits.
The picture above displays various circular knitting needles and some useful bits and bobbins. Number (2) is a regular circular needle, made of wood. Number (3) and (4) are parts of an interchangeable circular knitting needle, allowing you to replace parts and building the circular needle as you see fit (longer or shorter cable, thinner or thicker needles). Number (6) is an assembled interchangeable circular knitting needle.
Number (1) is a knitting doll, used to knit cords. Number (5) is a view measurer, used to measure the size of knitting needles. This particular measurer also has a ruler with a view window, making it easy to check the gauge of your knitting. Number (7) are markers, used to mark specific locations in your knitting. Number (8) are row counters. You put them on your needle, next to your stitches, and each time you pass the row counter, you twist it once, and it will keep track on the number of rows you've knitted.
Number (1) in the picture above are yarn needles, with a big eye. This makes it easer to use them with thick yarns. Number (2) is a regular scissor, used to cut yarn (although you won't need this too often, I hope). Number (3) are pom-pom makers, which are used to make pom-poms (but you can also make pom-poms without an industrial pom-pom maker).
Number (4) are straight knitting needles, which is no favourite of mine, as they hurt my shoulders because they are too long. If you need room for a lot of stitches, I recommend circular needles rather than straigth needles.
Number (1) is a tape measure, very useful when knitting garments such as sweaters etc. Number (2) is a regular safety needle, which can be used to hold a couple of stitches. Number (3) is a larger, blunt safety needle, designed specifically for holding stitches. Number (4) is a stitch holder that allows you to access the stitches from both sides, which can be useful at times. Number (3) won't allow this.
