state of the art for bounties?

Is there a state of the art for free software project bounties? I’m sort of curious, because I’ve become a heavy user of a project which has an overworked maintainer and no particularly vibrant community.  I also  have no time/ability/desire to dive into that codebase, but I have two features that I’m pretty sure upstream would accept if someone coded them up. So I’m sort of curious about the options for situations like that, but realize I haven’t looked at the problem in ages and don’t know what the state of the art is, or if any one is even experimenting with it anymore. Anyone? Bueller?