Don't eat out.
Realistically, I have a couple of pre-scheduled dinner dates. However, where possible, I'm going to reduce my restaurant spending this month. More excuses for potluck!
I don't use cash very much, so coin jars don't fill quickly. However, in June and July I'll put extra change into a big jar and add the total to our Big Vacation fund.
While we don't have enough for a garage sale (nor would our location allow for that), there are several things that don't need to live in the apartment or in storage anymore. I've listed a couple of spare items on Craigslist, but haven't kept up with them. In June I will pay more attention to those listings and add a few more, and save any proceeds for grad school.