McMaster-Carr

Mcmaster-Carr is a site I use a lot and it is very user friendly, to search and navigate through, order and check out. Everything is categorized but you can also enter in a search and it will come up that way too. So you do not get frustrated searching for the item you want. They use a list of items on the left as well as a thumbnail picture on the right ,this is particularly helpful if you know what your part may look like but are unsure of the exact name of it. Gotta love pics. All contact, account and help is along the top to help as well.