I'm building persumi.com for writing/blogging, and rizz.farm for doing lead generation on Reddit.
Built persumi's MVP in three months in my spare time, and rizz.farm in six weeks in my spare time (but haven't launched it).
I built both projects out of my own needs - persumi for replacing my own blog, and rizzfarm for promoting persumi, hehe.
Might start a 3rd one soon (as I like to tinker) though I haven't found a problem to solve yet. :)