FLAN-T5 is a finetuned version of Google's popular T5 model with instruct-finetuning. As stated in the model repository's introduction, compared to T5, FLAN-T5 is "just better at everything." With its permissive license, FLAN-T5 has become a popular option for a starting instruct model.
MPT-7B and MPT-30B are a set of models that are part of MosaicML's Foundation Series. Trained on 1T tokens, the developers state that MPT-7B matches the performance of LLaMA while also being open source, while MPT-30B outperforms the original GPT-3. In addition to the base model, the developers also offer MPT-Instruct, MPT-Chat, and MPT-7B-StoryWriter-65k+, the last of which is trained on a context length of 65K tokens.
Further reading