I've made a site which lists all WWDC talks since 2000.
It doesn't host the videos, but has some details for all the sessions, organised per year.
I find it very useful to get an overview of a technology, to figure out which year introduced some new feature.
All the data on this site is also available as a single JSON file.
If you do have access to your own video files, there's a video player that you can configure with some parameters.
Tip: Use CMD+F on the “All" page to search all of WWDC history.
A lot of WWDC talks are no longer shown on Apple's website, but the video files still exist on the CDN.
In WWDC Index, you can configure $streamUrl in the video player to play those files.
If you want to download the available talks (before they are taken offline), I recommend this excellent gist with download scripts: http://gist.github.com/IsaacXen/874c59aec92a13f30728aecdabb9ea80
Once you have the files locally, you can use $videoAlmostEvery in the WWDC Index video player to use the filename from those download scripts.
All WWDC sessions since 2011 are available for public streaming from Apple. Some sessions from 2007, 2008, 2009 can be viewed after logging in with a Developer account.
This graph shows how many WWDC sessions are still in the Developer app, available for streaming, require a download, or are not available from Apple.
For an overview of all WWDC sessions, see https://nonstrict.eu/wwdcindex/
Apple has uploaded a new batch of videos from last years' WWDC to YouTube. Now that most videos from 2023 are on YouTube, I've added a YouTube embed in WWDC Index.
So now you can watch videos directly inside the website. But of course you can still customize the inline video player to point to your own source of videos, for older videos.
Tom Lokhorst