I too am from the St Louis Area (Collinsville and Highland, ILL) and have never found a decent RV rally anywhere near. Since moving to AZ NO 1 is Quartzite, 2 Moab, 3 just name a place and some will showup.
About what happens at a house party. The major difference at an RV rally is that everybody brings their own house. People eat too much, beverages of all types are imbibed, people sit around and chat about their rigs, the state of the world, their grand children and things they have done/seen recently. There may be games, campfires, sing-alongs or whatever. Depending on what the area has to offer, there may be sight seeing trips, golfing, etc. Maybe even professional entertainment. Some rallys have catered meals while others will feature pot luck dinners. In short, there is no standard RV rally format.
It really depends on the folks organizing it and the desires of the attendees. Our RV forum rallies tend to be free flowing, with little in the way of organized events beyond an afternoon "social hour" each day and ad hoc dinners (pot luck or dine out). Other clubs go in for gatherings in venues that have entertainment, catered meals, etc. It all depends on what you are most comfortable with and find most enjoyable.
Try contatcing a local Good Sam club in your area and see if you can come to one of their rallys. Most GS chapters have arally somewhere every month. But if you do not find it to your liking, don't write off rallies altogether - just try some different ones.
Many RV manufacturers put on rallies with various activities, education and entertainment. Often, they'll have a team of techs on hand to perform repairs. Also in attendance may be techs from the suppliers of various RV appliances and systems. For folks with a motorhome, FMCA (the Family Motor Coach Association) organizes some large rallies which are a larger version of the manufacturers' rallies.
You can view activities from some prior RV Forum rallies by clicking the Photos button above. Photos from the 2006 Quartzsite rally can be viewed here. (Reminds me I didn't add them to our photo gallery).