-
hacktoberfest
Discontinued Hacktoberfest - App to manage the annual open-source challenge, used for the 2019 & 2020 seasons. (by digitalocean)
-
InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
I would start at First Timers Only and see what they have that you can do. Every October there is Hacktober, and they have a good page for getting started in Open Source.
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.