I'm a patron of a number of people who have full-time jobs and do what I know them for on the side.
Another option is librepay too. Check the recent Patreon thread for alternatives and comments.
Why do you think you can't or shouldn't?
I.e. my manager is quite open about 20% of time arrangements, and we are working on several open-source projects at work, but I am not sure if taking money for working on something extra wouldn't violate something. It might be worth it to have it clearly spelled out in the contract.
On the other hand, a.f.a.i.k. in what do you do in your free time on your own hardware should be no concern to your employer, so accepting patreon donors should fall into that category as well?
Alongside patreon, I would attempt to introduce something like Varnish Moral Licence [1] as well. It looks like Mr. Kamp figured a nice way how to get a open-source sponsorship from big corporations (because from the procurement's perspective it still looks like a licence you get an invoice for even you don't promise them anything in return :-)
[1] http://phk.freebsd.dk/VML/vmlfaq.html#isn-t-this-more-a-sort...
