This is one of my all-time favorite recipes for cucumbers--if they are homegrown, even better.
It comes from the Better Homes and Gardens Cookbook (the red and white checked one) which is my personal favorite basic cookbook.
For marinade combine in a covered container:
1/4 c. vinegar or lemon juice (I use white vinegar)
1 - 2 Tbs. sugar
1/4 tsp. celery seed
1 large cucumber, peeled and thinly sliced (3 c. worth)
1 small onion, thinly sliced and separted into rings
Toss to coat with marinade.
Cover and chill for 2 hrs. or up to 5 days.
You can also add a little diced tomato to it, which is quite delicious also.