I want to read any fic with Maggie Walsh as Riley Finn«s biological mother.

There's Wet and Wild by Chelle.
Summary: Spike is captured by the Initiative again and Buffy has to join to get him back. This is set DIRECTLY after Something Blue so Hush never happened.
I'm pretty sure Maggie is Riley's biological mother and raised him in that one. Spike's human past is completely non canon though.
It has a one shot and oh so sad sequel called We made love .