Try DarkTable and RawTherapee. Both of these options are pretty decent open source alternatives to Lightroom for the majority of basic workflows and common cameras.
I'd say they both are more than adequate, and allow for some pretty advanced workflows, since they expose a lot more tools with more fine-grained control than Lightroom.
For anyone who tries these programs, many of their developers and users hang out at https://discuss.pixls.us/
