Alright, let's add some more here:
Kiddy Girl and- episode 1 has it. Here you get graphical hints and it is made a sub topic of the episode.
The main character wears bloomers (with a waitress uniform), which other girls disapprove of. After some quarrel she just takes them off in rage without being fully aware of what she's doing. When she continues her job she suddenly realizes the missing layer and goes like "oops!". As if that wasn't enough, some villains attack and she puts on a fight with lots of stunts and flying maneuvers, all nopan.
Another instance is B Gata H Kei episode 5. This entire show, despite its content focus, is graphically very unexplicit. The nopan element is made the main topic of the second half of the episode.
The main chara of this show usually thinks of how to seduce guys. In the second half of this episode she gets the idea that going to school nopan might totally attract the guy she admires. Obviously she is very conscious of that, talks to her (female) friend and asks the guy how he finds girls being nopan - who gets an accidental flash at the end of the episode.
Bakemonogatari is on top of the Approval list in the nopan tag section, but actually the element is totally covert here. A few seconds are graphically explicit, but it is not made a topic at all.
Firstly in one of the episodes there is a little talk on what the guy would think of 'her' not wearing panties under her leggings which she is wearing under her skirt. Perhaps some voters counted that already. Then, in episode 15 [coalgirls], a white haired girl comes out of the ground, beats up some bad guys in a couple of millisecond-scenes and disappears again. Doing some seriously fast stop-play-clicking, one can actually see some nopan scenes, with one front shot where she's "wearing" a plaster. Took me some effort to make out the scenes, especially since it's number one in the rating.
Seitokai Yakuindomo has two, one in episode 3 and one in episode 4, both with no graphical explicitness. The nopan element is mentioned by the characters, but it is not made a topic beyond that.
In episode three one chara didn't put her bra and panties on under her dressing gown when they came out of the onsen (on a school trip) because she doesn't wear underwear at home either. She says it when the items were found left behind. In the next episode they still wear winter uniforms (last day) even though summer began, so one girl goes nopan to better withstand the heat, but this is not mentioned again after she tells it a (male) friend.
Edit: In episode 11 there's one more of these "it's mentioned but that's it" moments revealing that the same chara as in episode 3 is nopan at school. She says so herself, though it's not clear if it's a prank or not. Just for the record.
In Manami & Nami Sprite the first out of two episodes takes the nopan as a topic of the episode and is shown rather explicitly at times.
Manami is a shy girl but has a split personality, with a really tough woman (Nami) as her second personality. In the first episode Nami beats up a few girls who took her panties to tease her. On the next day these girls steal her underwear from the locker when she's in swimming class and she has to spend the rest of the day nopan, with the villain girls trying to reveal it.
In Renkin San-kyuu Magical Pokaan episode 1 we get a little nopan flash for unspecified reasons. Graphically rather unexplicit.
A main chara girl uses magic, which lifts her skirt, under which she is nude. The scene pretty much ends after that. Also, there is a "nopan delivery service" - just for the record (the show is truly horrible, don't start watching it).
In ToLoveRu Trouble OVA 6 there's a nopan, which is made a subtopic of the first half of the episode and which is made graphically explicit in a final accidental flash. Btw: We also get a number of graphically highly explicit no-bra scenes in OVA 4.
In an initial fight Ru's panties are cut off, which she only notices later (she's at school with the school uniform). After she spends some time at school worrying about that, the situation is resoved with a final nopan flash outside, which is, of course, seen by 'her' guy. In OVA 4 she is "graphically nopan" as shown from side views, but at other times there are pantsu flashes that reveal this to be a (wanted) graphical error.
In Ghost Talker Daydream epsiode two there is a (graphically unexplcit) nopan moment that is made topic of a few minutes of the episode.
The main chara promised to sell her (used) panties this day and since she forgot, she provides her current ones, which leaves her nopan for a couple of minutes (sounds pretty lame but the show is quite decent).
Kiss X Sis has two. One in episode 2 and one in the second part of episode 7, both made minor subtopics and both being pretty graphically explicit.
In episode 2, highly graphically ecchi, by the way, 'she' takes off her pantsu because they got really wet (yes, in 'this' way), so she's nopan at the very end of the epsode. In episode 7 a women wants to try on the training suit of 'her' guy, does that without any underwear on and ends up masturbating in it (this show is a borderline-hentai, so to speak).
Alright, so much for today. There's more to come.
