If you want a dynamic interface for talking to virtual characters, Charstar is a good pick. Built on open-source AI, Charstar lets you generate, discover and chat with a broad range of characters, each with its own personality, history and skills. The interface supports a lot of nuance and context, so if you like interactive fiction and role-playing, it's a good match.
If you want a constantly changing selection of AI characters, check out Inworld Arcade. It's an immersive chat interface with a variety of characters, including historical figures, celebrities and fictional characters. New characters are added daily, so you can have a lot of fun and learn a lot, too. It also lets developers create and integrate their own AI characters, so it's a good pick for interactive storytelling and socializing.