Local vacinity Wehrspann Lake in April is good for crappie. The normal minimum is 10 inches there, but in April they drop the size limit. There's still a limit per the number you can keep at 10 total. I take my kids out there when we've only got a couple of hours and we usually catch our limit of 9-10 inchers. Just use a minnow and a slip bobber in about 7-12 feet of water. If you don't have a boat, fish off the pier on the south side of the lake. The crappie hang out around there.
Standing Bear Lake is stocked with trout in the fall and they'll survive till the water gets close to 70*. They'll bit corn, powerbait, or minnows.
Other than that there are numerous places in Iowa that people are unfamiliar with. Cold Springs, Lake of Three Fires, Viking Lake, Horse Creek WaterShed. Panfish, catfish, bass
In Nebraska you have Summit Lake, drained and dredged a few years ago, I haven't tried it since. The best place for walleye is up by Decatur Ne.
Branched Oak used to be good for walleye but has since silted in. I haven't fished there in years.
Your best places of all are farm ponds though. They don't get much pressure.
Unfortunately public fishing areas within 20 -30 miles of Omaha (on the Nebraska side) get too much pressure and people keep things they shouldn't. I was out at Cunningham years ago and watched an Asian family with a 5 gallon bucket keep over 30 bluegill, white bass and crappie that were maybe 3-4 inches long. Everything they caught went into the bucket and there was no way you could get a fillet off those things. They had to be eating the whole fish head and all. It's worth it to spend the extra money and buy a non resident Iowa license and go the 30 - 40 miles east and fish over there.
BTW I left Prairie Rose of my list.
Another not so common fact is the State of Nebraska stocks farm ponds at the request of a farmer. If the state stocks it the farmer has to let you fish it. The only loop-hole is you have to ask the farmer for access to the pond and they don't have to let you cross their property to get to it. In that case file a complaint with the Game and Parks and they'll stop stocking the fuckers lake at your expense.
There is a list of all state stocked farm ponds.
Try Offutt AFB lake that is south of Bellevue. When I was growing up there, we used to bring home stringers of crappies in the spring. Lots of rocks on the southside and they would be loaded during the spawn.
I wasnt really into bass fishing but also heard there were a few decent lips pulled out on an occasion. I think I heard a majority of those bass that were caught were near the stables. Now, its been about 15 years since I been there so I dont even know if all of that even exists.
Typically as Red mentioned.........farm ponds whether stocked or not will be gold mines........little or no pressure.............I love throwing a weightless Zoom trick worm in Merthiolate, bubble gum or white and just watch them explode on it.