StarCraft
Mods
ChaosLauncher - ChaosLauncher allows you to run SC1 with all the necessary mods like Windowed-Mode.
W-Mode - Allows you to play StarCraft 1 in windowed mode using ChaosLauncher.
Resources
ICCUP - Official ICCUP website - they're currently the biggest non-Korean organization with a ladder system for organized play. You can get StarCraft 1 legally and free only from here.
TeamLiquid - Great resource for keeping up with SC1 news.