Once a week I take my bike to the local supermarket to do my shopping. My panniers fill up really quickly and I always end up with bags on my handlebars (for UK people - the bags I'm talking about are the big blue Tescos reusable ones). Even with a backpack thrown into the mix, I still need to carry at least one bag, usually.
I know that there are plenty of easy solutions to the core problem (shop more often, take the bus, persuade a friend with a car to drive me there, etc) but let's look at the more fun side of things: what's the best way of getting a very large amount of shopping on my bike. I have a rear rack so suggestions for really big (backpack sized, large shopping bag sized or bigger) panniers and rack boxes would be useful, but let's not limit it to just that.
Also, if you do your shopping on your bike and have a similar problem, what do you do?