Oh I've had loads (and still have) of projects that got me to learn cool stuff! To keep them separate, I'll post some in different rants.

The thing that has helped me most over time (it didn't teach me cool things but it's very useful in general) is that, when api's have rare limits and you need/want to use them more often than is really allowed: you write your own alternatives.

I've especially had this with a geoip api's. Needed one for nearly every project but hit the rate limits with every goddamn service.

Wrote my own in a weekend and no rate limit hitting since then!