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.
RedPajama-INCITE is the first family of models trained on the RedPajama base dataset. The goal of the RedPajama-INCITE models is to replicate the LLaMA recipe but make the model fully open source under the Apache license. As of the initial release, the 3B parameter model is best-in-class, with the 7B parameter model in progress. Update as of June 6, 2023: the 7B parameter model was made available, outperforming other models of the same size.
Further reading