Makes a good slug bait. Place it in a shallow pan, can or container near your plants that are susceptible to slug damage: Hosta, Toad Lily's, etc. Bury the container in the soil, so that the lip remains above ground level.
The slimey things will slither into the alcoholic pool to imbibe. They never make it out! Until you remove them. Ugh!

Here are some links that might be useful:

How to use beer for garden maintenance

Sustainable gardening: garden snails (and beer)

Unusual uses for beer

I found flat beer to be a very effective fertilizer for my fig tree... but unfortunately I can't say what effect it had other than to make the fig grow upwards (instead of thickening out).

Best of luck with your excess beer!

I pour a can into the slow cooker when I do pot roast (instead of water). Yum.

Thanks for the suggestions- looks like I'll have to hang onto it till spring!

When I was on a Jerry Baker kick, I bought all sorts of "homey" ingredients, including beer, to make his tonics.

I ended up being a slacker and just poured the beer in my compost. I don't know if it was good or bad, but I still had lovely, wormy compost!

i saw some gardening show on TV several years ago where a guy mixed beer with green dishwashing liquid (NOT anti-bacterial) and ammonia to make a grass/lawn spray that was supposed to really promote growth.

to this day, i haven't managed to find the recipe again, but ... those were the three main ingredients i remember. this could be an option for you - since lawns don't really care if beer is skunked or not ;)

(but then again, IMHO, the goal of a gardener is to minimize and reduce grass in favor of native plants :)

Satellitehead, the person you must be thinking of is Jerry Baker, as mentioned in the post above by bagsmom. I had forgotten about him- Googled his name and came up with all sorts of help.

Beer gone bad, not around my house, yes beer is best fresh, unlike it's fermentation cousin from the vine age is no friend, but as long as it hasn't taken excessive heat it should be fine for some, Maybe it just was not his usual brew, But if I was to put it on my plants I would process it internally first, but don't overdo it on any individual plant, would not want any nitrogen burn.