Fal.ai
Developer API platform for running image, video, and audio generation models (Flux, SDXL, Whisper, and more) at low latency. Popular as a serverless GPU layer for multimodal AI apps, with a clean Python/JS SDK and pay-per-use pricing.
LangChain
Most widely used framework for building LLM applications. Chains, agents, RAG pipelines, and deep integrations with 300+ tools.