This is just a list of places that you can generally rely on for parking your RV just one night, maybe three nights. It's always a good idea to ask for permission, even if listed here. Of course, smaller RVs have more options.
NOTE: Not asking for permission, could result in a ticket with fines, so be fore warned. Be smart, get permission more often than not.
Big Box Retailers
Like Walmart, most Kmarts, Best Buy, Sams Club and others will often allow free RV overnight parking. Ask the manager to be safe. Remember, local ordanaces may not allow them.
Rumor is that most allow member parking if you call in advance for permission.
Many offer cheap RV spaces when not hosting events.
Many organic farmers enjoy having guests, and appreciate it if you buy some of their crops. Some even have nice markets on property. Ask permission and often your good for 1 to 3 nights.
Elks, VFW etc. often allow members free or cheap RV overnight camping.
Many larger golf course will allow RV overnight parking, just ahead for permission. They are generally happy if you golf, buy some gifts or dine at their restaurant.
It's rumored that many operators will allow overnight RV parking, Ask first.
Hotel Parking Lots
Many will allow 1 to 5 nights for a $5 to $10 fee. This will be dry camping with no hook ups. Just ask, 3 out of 5 smaller ones will allow it.
Go for an after dark show, and ask the manager if you can stay the night because it's a pain to drive at night in your RV and your tired.
If you spend some money on drinks, ask to stay because you want to be a safe driver.
A few offer free or low fee RV camping. Check City, County, State, and Community parks. Each will be different by type and state or location.
Naturally, rest areas allow a few hours of free parking. A few allow overnight RV parking. Check the rules for the subject state.
Roadside Parks & Picnic Areas
Not often, so make sure first.
If you see a number of trucks parking, your golden. No need to ask, but be courteous.
Vehicle Repair Shops
Call ahead, for an appointment to see a mechanic in the early morning to check something. If you have an appointment, your golden.
Some, not all allow overnight RV parking. They are subject to city/county ordinances, so always ask first.
Many wineries are avid marketers and know that RV owners are likely customers. Call ahead at larger wineries and many will allow permission for 1-3 RV overnight parking.
Frankly, this list is not complete, so I will be adding more as I think of them, and see them added in comments.
NOTE: In many of these locations it's best to keep a low profile, avoid using slide lever jacks and other things that spell camping, unless your certain or ask first. Also consider your security and be prepared to find an alternative location if the area makes you uncomfortable in any way.