Q: What are mucus laden, hermaphroditic boneless creatures who can stretch up to 20 times their length and eat holes in your garden?
A: SLUGS. There are hundreds of varieties, each one gooier than the last, and they all want to use your garden as a cesspool.
Luckily, there are lots of creative ways you can rid your garden of these gastropods. For one thing, slugs love beer. They're attracted to the yeast and sugar, and if you fill a shallow dish up to .5" from the brim with beer, the slugs will come sniffing and drown themselves. Apparently, slugs prefer cheap American brew like Budweiser, Coors, and Michelob. Be sure that the lip of the dish is flush with the ground, but that the level of beer is half an inch below the lip so they can't crawl back out.
If you really need to work off some of your frustration, you can go guerrilla on them by picking them off at night with a flashlight and dropping them into a cup of water with a little dish soap. If you're feeling especially nasty, make it salt water. Again, this must be done at night as slugs are nocturnal.
Another popular and extra-nice way to get rid of slugs is by using copper tape to create a boundary that the slugs will not pass. Something about the ions in the copper drives repels them. While this is effective at keeping out more slugs, it doesn't help that it essentially traps all the existing slugs (and their eggs) which are already in your garden, barring their way out. I have also heard pennies being used to surround seedlings with moderate success.
There are some other pretty stinky and/or toxic options, such as the use of diatomaceous earth or pesticides. A repellant border of crushed ginger, coffee grounds, lint, espson salts, seaweed, lemon balm, or wormwood can also be used. Some plants are naturally abhorrent to slugs and can be planted in a border around a slug-prone bed. Some of these plants include fresia, red cabbage, daffodils, rosemary (and any other pungent smelling herb), corn, chard, hibiscus, azaleas, and sunflowers.