ChatGPT
"ChatGPT is an AI-powered language model developed by OpenAI, capable of generating human-like text based on context and past conversations." GPT 3.5 is free to use after sign-up at openai.com. GPT-4, the latest version, is available through a paid subscription.
Google Bard
"A conversational AI tool by Google. Collaborate with Bard to brainstorm ideas, spark creativity, and accelerate productivity." Bard is an experimental AI powered by PaLM 2 and free to use.