Endion Park, 16th Avenue East and First Street.

There are a couple of courts on Park Point by the community center that are almost always empty. They aren't in the best of shape, and it is easy to hit the ball into the poison ivy on the lake side. You might want to bring a broom too.

The Park Point court (just one) got an update last year with a new net. But it definitely needs help (and a broom). 
The Longview courts on Fourth Street are technically free, but you have to pay or join Friends of Tennis if you want to make a reservation.

Upper Woodland, by the community center off of Winona Street. I think the ones on E 4th/N 25th ave E are free as well.

The courts at Wheeler and UMD are both good. The courts at Marshall are good and rarely locked in my experience. Not sure about Woodland or Irving. The courts at Harrison are pretty bad.

Uh, no they're not.  They were redone last year.

Speaking of tennis, other than the creepy platonic Craigslist category, how would a person find someone to play singles with?  Anybody have any ideas?

What's the deal with those Longview courts? Can you just show up and play if there's an open court? Who can use the building? What's in the building? Why does it look like a private club? Is it owned by the city?

Well glad I found this informative page on where to play, now about that informal league/phone list/club/something .. Did anyone ever start anything??

Thanks!