A veritable treasure trove for the amateur or professional cook is Sous Chef. You can search by cuisine, by specific ingredient or even by technique such as smoking. You can find all manner of hard to find ingredients. You can also order your tableware or equipment from this well laid out site. So popular is their Ottolenghi 'Jerusalem' set to save you trawling through the long lists of ingredients, it is currently sold out. Genius!
Another of our favourites (their restaurants are phenomenally good) is the wonderful Brindisa that focuses on Spanish ingredients. We particularly love their saffron and pimenton, the cheeses and hams are also to die for. Lovely to browse it's a very user friendly website. Check it out.