Well I've taken a look around the internet (it needs a good dusting) and can't really find too much. I've posted a bunch of the featurettes I've found on the spot and here is a list of the easter eggs taken from Buffy-boards.com This is an excerpt from a post by Kinslayer

"Season 7 disc 6

1. Select Special features and press enter.
2. Go to featurettes and press enter.
3. Press left and a large B will appear, Press enter.
4. A quick montage (36 seconds!) of scenes mostly featuring heroes and villains from the series will be shown.

Season 6 disc 2

1. Select the episode 'Once More, With Feeling.'
2. Go to the 'Language Selection' and there highlight the menu entry 'English for the hearing-impaired.'
3. Press the 'Left' arrow key on your remote control and the Buffy 'B' will be highlighted. 4. giving you access to 3-minutes worth of footage from the soundtrack signing at Tower Records in Los Angeles.

This one bugs me. On my disc you highligt “resume episode” and press up to highligt the big B. And it´s only 1:40 of highlights!

Season 6 disc 5

1. Select the episode 'Normal Again'
2. Go to the 'Language Selection.'
3. Highlight 'English for the hearing-impaired' and then press the 'Left'.
4. You will now see a sign saying that there is a 'Computer Download' available for the episode call sheet

I don´t have this at all!

Season 6 disc 4

1. Go to Doublemeat Palace.
2. Go to language menu.
3. Highlight resume episode and press up to highlight a B.
4. Press enter to find out how to access a call sheet for the episode normal again."

I'll keep looking for anything from the bonus disk for you and if I find anything I'll post it in the vids. ;F

thankss soo much ArabellaElfie!

No problem, sorry I couldn't find the rest for you. I'm still on the look out

Found something! It's slightly cut off at the end but this was the first time I found it so I posted it up. This is just more of an easter egg but it's the special promo from The Gift with scenes from the first 100 episodes. You will probably recognize it. Tons of people insert it into their vids but it's really hard to find solo. I'll still keep you posted if I find more.

link