You can put them round the base of plants as a mulch, or add them in layers to your compost bin.

Good for acid loving plants such as Acer palmatum, Camellia, Skimmia, Azalea

Slugs and snails really dislike them!

You can use them instead of beer in a beer trap for the slugs and snails - there are better uses for beer.

I've heard lightly sprinkling used coffee grounds over your lawn will feed it.
Don't know how true this is though.

I'm just wondering how you'd 'sprinkle' coffee grounds - they're usually a solid sort of mucky, wet clump;-)))

Dry them out first I suppose?

Hmm, well I'd avoid putting them on the lawn, cannot see what possible good they'd do - they're quite acid for a start, so I'd be using round my acid loving plants.

I always tip them onto the roses. Does it do any good - no idea, but the roses look ok.