As the first Weekend Challenge closed about 18 years ago, there isn’t that much left of it. However, you can find the remains right here:
The theme was “contact” and it was won by imgrandpaboy.
If you’d like to check out other past challenges, I’m trying to maintain a list of all the themes, so the winners can find a (more or less) unique one each week: https://www.geoxis.de/blend/themes.htm