Valve's Portal is free for PC and Mac gamers until May 24th!

[Maiandra]

I'm glad to hear you liked it, Andrea. It's awesome! I too tried playing the original HL and lost interest partway through. I think the references to it in Portal are more for the sake of humour (with Black Mesa as a competitor for Aperture Science) than any true plot relevance.

[MusicallyInspired]

Aperture Science is also a major part of the upcoming Half Life 2: Episode Three. It was mentioned at the end of Episode Two as the destination of the next part. It's nothing to do with Portal, though. Kleiner states that Aperture Science were their competition to compete for government granting or something and in their race to beat Black Mesa they crossed some lines they shouldn't have.

And yes, Half Life 2 is loads better than HL1 (which was innovative at the time).