I have recently been asked where a person can buy sewing patterns. Well, the most common way, is to go to a large or independent fabric shop, browse through the pattern catalogs, and select and buy your patterns right there in the store. When I worked for a pattern company, it was standard for the big companies to have approximately 700 patterns in a catalog, so there probably is some version of what you are looking for in one of those books. The most common catalogs you will find are Butterick, McCalls, Vogue, Simplicity and New Look. In the catalaogs, you will find patterns for children, women, men, boys, girls, infants, pets, crafts, and home decor. Sleepwear, formalwear, casual and costumes are all represented.
If you are not near a fabric store, you may shop online, or you can buy books or magazines containing patterns/directions. You can also invest in a computerized pattern drafting program. (I have no experience with these)
My recent post on the subject of pattern companies gives lots of other pattern choices, and here are a few more, I've found along the way...
Nostagic Patterns is a new vintage-inspired pattern company.
Men's patterns can be harder to find, and Islander Sewing systems has plenty.
Of course, if vintage is your thing, there's always www.oldpatterns.com.
So, let's say you've found the perfect pattern, but you can't find the notions and fabrics required to make it. You can absolutely shop online with good results. I would recommend getting swatches before ordering blindly. You may have to pay a swatch fee, but that beats ordering fabric you don't want, doesn't it? Some stores in Manhattan's garment district will handle your swatch requests quickly and easily, and you can order beautiful fabric without hassle. You do have to be able to describe what you want, though. If you live in New York City or nearby, you can't do better than hopping on the subway.
Some ideas for where to buy notions:
For fabrics, the list is truly endless. Here are some I've used and loved: