I like the list of "bounties with no deadline (which is based on Puzzling and Code Golf equivalents) on Literature, so I am stealing it with attribution; this is almost completely copied and pasted from the other site.
This is a list of unofficial, deadline-less (hence not searchable) bounties offered by users on various challenges on the main site.
The list need not be limited to questions that already have an answer. You can offer bounties both for your own questions and for other people's questions.
Disclaimer: There is no guarantee that the user will award the bounty for you in case you fulfil its requirement. Especially if the user isn't an active member anymore. The only guarantee is their written word.
Guidelines for updating
- To add a bounty, create an answer that contains a link to the question that needs a (better) answer and the bounty you are willing to award.
- Answers can be sorted to see which bounties are newest.
- Please comment on answers if you notice that there’s been a good answer to the question in question for a while that the bountier apparently hasn’t seen.
- If a bounty is awarded, delete the meta answer.