Well, since you are actually on this site you should know a bit about what anime and manga are. Actually finding them is sometimes another matter though, and that is why this section is here. Particularly in the UK where I am, getting hold of them can be hard if you don't know where to look. To help remedy this I've collected a list of online stores that sell anime videos, DVDs and manga comics and graphic novels.
For people shopping in the UK high street the most common stores you will find that stock them are HMV, Virgin Megastores and Forbidden Planet, all of which have online stores as well. The first two only sell anime and usually have a moderate stock, which is sometimes miss-labelled as 'manga' thanks to Manga UK's position as one of the UK's two biggest anime distribution companies alongside ADV. Forbidden Planet sells both anime and manga and usually have a good selection, but tends to be a little more expensive.