There are a few sources on the Web where you find great collections of datasets, code, and advice. Some of them are listed here, let us know if something is missing.
A nice and relatively recent collection of recommender-system tools and best practice guidelines maintained by different persons at Microsoft. To the best of our knowledge, the collection was first introduced at the ACM RecSys Conference 2019  by Graham et al., and later presented at the Web Conference 2020 by three different authors, i.e. Argyriou et al. .
 S. Graham, J.-K. Min, and T. Wu, “Microsoft recommenders: tools to accelerate developing recommender systems
,” in Proceedings of the 13th ACM Conference on Recommender Systems
, 2019, pp. 542–543.
 A. Argyriou, M. González-Fierro, and L. Zhang, “Microsoft Recommenders: Best Practices for Production-Ready Recommendation Systems
,” in Companion Proceedings of the Web Conference 2020
, 2020, pp. 50–51.
RecSysWiki was a Wikipedia-like website to which everyone could contribute. The wiki was founded in 2011 by Alan Said. However, as far as we remember, contributions from the community were not very frequent and in April 2018 the RecSysWiki announced that the Wiki was down. Since then the Wiki seems to not have recovered, as both http://recsyswiki.com and http://wiki.recsys.acm.org/ lead to websites without content.