I just see way too many of them and a lot of them are done poorly. Here's the only two "easy and fun" map I liked a bit (that I can recall):
http://www.steamproxy.net/sharedfiles/filedetails?id=86594540
http://www.steamproxy.net/sharedfiles/filedetails?id=292030632

also, what's with the negative connotation towards "easy and fun" maps? we enjoy making them, others enjoy playing them. they dont have to be challenging to be fun.

I always thought it was fun, and not serious, to "play level designer" by not only making an initial layout but tweaking existing and listening to feedback if you are doing good or not. It's also fun to see your test subjects boggled how to solve a test, if you can achieve such a feat. Nothing cripplingly difficult but something rather difficult in the test subject's mind to comprehend.

the level i just made has you in mind by the way. i overkilled the gel intentionally.

by serious i mean serious though into making it, regardless, the campaign was easy for me, minus one level, i didnt realise i had to use the repulsion gel from the previous chamber.

Some people consider more challenging maps serious maps, like you, and I don't know why. It's either "easy and fun" or "hard and serious" maps and nothing in between. By that definition, the whole single player campaign (and maybe coop) would be considered serious but you had fun playing those, didn't you? There can exist "hard and fun" maps. When you and others try to create these "easy and fun" maps, theydon't allow the player to invest much time playing, so it ends up being a waste of time with little to no satisfaction getting through them.

Here's a couple of recent maps that were fun to play that offered some kind of challenge:
http://www.steamproxy.net/sharedfiles/filedetails?id=408613263
http://www.steamproxy.net/sharedfiles/filedetails?id=407997671

Here's a collection I put together that offers some of the best fun and challenging maps you may ever play:
http://www.steamproxy.net/sharedfiles/filedetails?id=378738534

i agree, i threw it together in like 20 minutes, but what's the fun in skipping it? its a goof-off map. would you prefer a serious one? i have a bit more difficult map as well.

DISCLAIMER:
Read my profile before reading the rest of my comment!

Not exactly a roller coaster map but still just as mindless. I can skip most of it just by portaling and air-straifing.

Try my SP map?
http://www.steamproxy.net/sharedfiles/filedetails?id=398483361
Try my COOP map?
http://www.steamproxy.net/sharedfiles/filedetails?id=376181211