After Buffy died, Spike helped out the gang in her honor.
Before Buffy died, she asked Spike to protect Dawn, and he tried his hardest to keep his promie to his lady.
When Buffy needed help in All The Way with fighting the vamps, he came right away.
Spike helped Buffy with her hands in Afterlife.
Spike helped Buffy defeat Angel in Becoming.
Spike helped Buffy in Fool For Love figure out how he killed the slayers.
In Once More With Feeling, Spike saved Buffy's life.
Spike tried to help Buffy in Dead Things, but she wouldn't let him, but he did let her take out all her anger on him.
Spike helped Buffy in Sprial
Spike made sure the demons didn't kill Buffy in Family.
Spike helped Buffy cheer up and fight the demons in Flooded.
Spike introduced Buffy to drinking in Life Serial (This may not have been helping, but Buffy looked like she was having fun)
Randy helped Joan fight the vampires in Tabula Rasa.
In Beneath You Spike wanted to help Buffy with the worm thing.