Obviously it's not your show if you can't remember the name of it.

"The Secret World of Alex Mack"

But the show was badass and Larissa is the UBER hotness.

Personally I liked:

What Would you Do?
Legends of the Hidden Temple
Ren & Stimpy
Doug
Salute Your Shorts
Are You Afraid of the Dark? (The episode with the evil demon that was released when the kids looked into the flame skurred me)

Eureka's Castle was cool, but sometimes it freaked me the fawk out.

Newer show that I really liked was Invader Zim. Easily above a lot of those great old nick shows.