Most species of tarantula are very docile and friendly.  The best beginner species are the Mexican red knee, Honduran curly hair, and the Chilean rose tarantula.

Most species of tarantula have mild venom that poses no significant medical harm.  Tarantula bites have been compared to a wasp in term of toxicity. However, you could have an allergic reaction to the venom and have serious health complications (especially if you are allergic to bees). This is why handling is not recommended. 

Tarantulas are really friendly creatures. They will not chase you and plot to kill you like some people think (blame the movies).