According to The Hollywood Reporter Carrey's official website won in the celebrity/fan site category.
Pitt's Make It Right video was honoured in the activism category and Kudrow won in the comedy series space for her series Web Therapy.
Film critic Roger Ebert was named 'Webby Person of the Year'. Organizers say that Ebert has "raised the bar for online journalism and writing through his poignant and wildly popular blog, Roger Ebert's Journal."
The Muppets also received a Webby for 'Best Viral Video' and Isabella Rossellini won for her experimental work in her Green Porno series.
Martha Stewart, Matt Groening and Arianna Huffington were among the Webby judges.
Comedian and Office star BJ Novak will host the 14th Webby Awards ceremony on June 14.