Product review!   This item is more for cats but can also be helpful for dogs.

Our year-old kitty cat Boo is quite the confident, outgoing girl.  That's what we wanted since our last cat, who I miss terribly, was the type to hide under the bed when there was any commotion, and with two noisy Corgis in the house I didn't want that again.  

Boo also loves to jump up on things, and was very fond of the dining room table.  She'd sit on it, pad across it, drink from our glasses and try to steal from our plates.  Yuck!  I love animals, but not in my food.  Many cats can be deterred by a loud hand-clap or shout, but Boo is mostly deaf so that does not faze her.  Moreover, she's a bossy cat and if you pick her up and put her on the ground, she takes out her frustration by boxing one of the Corgis (usually Maddie, bless her) about the ears.  No fun for my poor dogs. 

I tried the aluminum foil trick and it just made her curious.  I did some searching and found a product called SSSCat.

http://www.amazon.com/MultiVet-SSSCAT-Cat-Training-Aid/dp/B000RIA95G

It is a can of compressed air (or really some kind of gas) with a motion-sensor on it.  Kitty jumps on table, can makes loud hiss and sprays air in her face, kitty bolts from room in shock.  

I have to say it works great.  It would be a disaster for a shy cat; my dear departed Alice would have hid for days if this thing went off near her.  But for a bold cat it's perfect.  Boo stayed out of the dining room for an hour the first time she set it off, but she soon figured out her new parameters and now it keeps her on the floor.  We also bought her a huge cat climbing tree to give her a safe place to go.  The beauty is the cat does not in any way associate the punishment with humans, since cats can get resentful of corrections in a hurry.

And it works for Corgis too.  Maddie is a garbage-can raider.  We have a small can under the sink, and she is an expert at nosing open the cabinets, pushing up the lid, and making off with food wrappers.  I didn't want to lock the cupboards because she is good with her paws and I was afraid she'd scratch the cabinets to bits.  Hide this near the garbage can and it sends the dog trotting away.  After a few attempts they learn to just avoid the area.

Just a word of caution: if you have a very sensitive Corgi, this would NOT be a good idea.  Even though it's painless and harmless, it is a very strong aversive.  Jack never raids the garbage, but he somehow accidentally set it off and he came running over to us, jumping and barking to warn us of the huge hissy thing in the cupboard, and later when my husband walked near the area Jack became alarmed.  I also wouldn't use it on a puppy, who might be inclined to bark and bite at it instead of backing away.

I would also limit it to one or two key areas that you really need to keep a cat or dog away from, since I think if you overused it you could end up with a paranoid animal.  

Definitely a useful device, and at under $25 quite inexpensive.