I'd love to get acquainted with using PUMS data. What is a good, free training resource that I can use?
IPUMS USA is a popular alternative source of PUMS data. It provides microdata from the American Community Survey and decennial censuses, integrated across time, including both current and historical data. IPUMS provides various video introductions and data training exercises, all for free.
And here's the web-based IPUMS USA User Guide. Some of the content is getting a little outdated, but it's very complete.