Ano Natsu no Triangle:

Waiting in Summer:


[Particle (Carlos Toshiki)] Ano Natsu no Triangle

Random Sex in Summer:

Waiting in Summer:


[Imperial Chicken (Fujisaka Kuuki)] Noise Raw + English

You call that a Crossover:

Onegai Teacher:


[Fukada Takushi] Rakugaki Hon 2012 Ver fc2 Satsu Set

A Summer Night's Dream:

Ano Natsu de Matteru:


[Grace (Yokoyama Naoki)] A Summer Night's Dream

Senpai wa Sugokatta!:

Ano Natsu de Matteru:


[Kikurage-ya (Kikurage)] Senpai wa Sugokatta!

Downtime:

Ano Natsu de Matteru:


[ReDrop (Miyamoto Smoke, otsumami)] Ano Natsu No Okinawa-Hen

Seaons Greetings:

Ano Natsu de Matteru:


[LolitaChannel] Yuumei Chara Kannou Shousetsu CG Collection No.226

Fall of the Drunken Turkey:

Ano Natsu de Matteru:


[Grace (Yokoyama Naoki)] A Summer Night's Dream

Type 22:

Ano Natsu de Matteru:


[TYPE-57 (Frunbell)] TYPE-22

Senpai's Pinch:

Previews:
Ano Natsu de Matteru: Eps. 8

Senpai's Feelings:

Previews:
Ano Natsu de Matteru: Eps. 7

So da Drama:

Previews:
Ano Natsu de Matteru: Eps. 6

And Action:

Previews:
Ano Natsu de Matteru: Eps. 5

Senpai was Amazing:

Previews:
Ano Natsu de Matteru: Eps. 4

Yet another anime with a HighSchool of the Dead plug XD

Senpai Says...:

Previews:
Ano Natsu de Matteru: Eps. 3

Together with Senpai:

Previews:
Ano Natsu de Matteru: Eps. 2

Gone Wild:

Previews:
Ano Natsu de Matteru: Eps. 1

Not sure if Ano Natsu de Matteru takes place in the same universe as Onegai Teacher. But, it was worked on by a couple guys who contributed in its creation XD