First is obviously Kraglin messing around with Yondu's fin and whistle arrow, and injuring Drax with it (just in case anyone hadnt seen it).
Second is Stallone talking to some of the other Ravager captains saying its been too long and they should get back together. I didnt spot it at the time, but they're supposed to be the guys who were the original Guardians in the comics. Stallone is Starhawk, who brought them together originally, before the newer team of Guardians which came a lot later.
Third is the gold high priestess talking with another gold person, who says the council are unimpressed with her efforts to kill the Guardians, but she says she has created something that will do the job, as she looks over to a big golden pod, and says "I think I will call him, Adam". This is Adam Warlock, Thanos' nemesis and hugely powerful hero from the comics. He also had the soul gem, which may explain why we havent seen it yet. Basically, Adam Warlock is coming at some point and it'll be awesome.
Fourth was Star-Lord walking in on a now teenage Groot, whos bark sheddings are everywhere in his room. Quill is ranting at him about the mess and Groot is just playing a video game. Fun. Also probably means Groot will be back to regular size next time we see him.
Last one is back to Stan Lee talking with the Watchers, who are wandering off, bored of his endless stories. This calls back to the scene mid-way through the film, and the fan theory of why Stan shows up everywhere is he is a Watcher. One of the ancient beings who document the events of the universe throughout time.
Bonus: In the credits, theres some bubbles where the characters are dancing along with whatever song is playing, and in one of them its
Jeff Goldblum in full Grandmaster costume
. No one seemed to notice in my screening, but I loved it.
Let me know if I missed anything.