Are there any open source alternatives (I'm thinking Ruby/Rails/Sinatra) where I could throw up my own RSS read/sync server onto Heroku or something?
I'm going to spend some time looking at the two main Perl solutions, Perlanet & Plagger (used respectively by http://ironman.enlightenedperl.org & http://perlsphere.net).
* Perlanet - https://metacpan.org/module/perlanet
* Plagger - https://metacpan.org/module/Plagger
Failing that I may produce a custom solution with a feed aggregator library (for eg. https://metacpan.org/module/XML::Feed::Aggregator).