"Here We Go 'Round Again" is a time travel, but still Slayer Buffy/Vamp Spike.
Another one is "Memory Redux", by MadRog. The friendship comes later in the fic, but there is definite Spike/Xander friendship.
Mmm. Maybe "To Be a Kind of Man" by MeganPeta. It's Xander-centric ficlet,and his feelings about Spike post-season, but with a Spuffy ending.
I would NOT say that "Sanctuary" is a "friendly" Spike/Xander bonding fic. It's angsty and dark, but they are friends, and it's very well written. Also, it's all human.
"When Tables Turn" by C. Roxane has some Xander/Spike moments.
"Return to Me" by Jypz has a more accepting Xander.
That's all I can think of off the top of my head, sorry I can't help with the last one.
