Online Fabric Shopping

So today I went down to the (not-so-great-part-of-town) Market to have a look for the spotty fabric to alter the strapless dress. They didn't have anything remotely similar so I am thinking about buying fabric online. I haven't done this before as I like to feel the fabric and check the quality before I spend my hard earned pennies. I've been checking out a few sites recently and I've seen some really nice printed cottons. Plus I think this would be a good way to stock up on cheap muslin or similar for prototypes.
I'll add some of these to my shopping lists when I get time.