Please note if it is incomplete or a WIP

There's this one http://dark-solace.org/elysian/viewstory.php?sid=3562 this one is incomplete but is been updated.

There's also paradox by jackofspikes which is complete

Also there's a time travel section on dark solace http://dark-solace.org/elysian/browse.php?type=categories&catid=19

I don't know if there will be any here that you won't have read but I'll give it a go...

And Here We Go Round Again by Megan
Season 6, season 2 eventually. What if Spike, after Buffy cruelly rejects him in season 6, decides to take advantage of Anya in a different way?

The Keeper of Truth by Trisha
"There's always consequences." Spike is proven right when Willow's spell brings Buffy back, years from where she's supposed to be. He'd be bragging that one up, if Spike of season 2 knew what the hell Buffy was talking about.

Goes back to pre-series but obviously then covers into S1...
Anticipation by 2writers4spike
Having no idea how it happened, Spike finds himself back in 1977, reeling from a newly acquired soul and more guilt than most could handle. After dodging Drusilla, his main focus is getting back to his own time and back to Buffy in Sunnydale so that he can atone for all he's done.That is, until he sees the newly born slayer in 1981 and goes off in a new direction. Can he stop the events that brought misery to Buffy's life, or will he be forced to watch destiny destroy the woman he loves all over again?

Prologue to life/I Know You by slaymesoftly (this is a series)
Buffy gets sent back in time to meet Spike for the first time. Post Chosen/ Season 2

Convergence by salieri
Post-series Buffy and Spike have a surprising meeting...in BtVS S2.

The Butterfly Effect by cousinjean
Five months after the events of "Chosen," a still grieving Buffy must follow a time-travelling demon back to 1997 (circa Season 2) Sunnydale to prevent him from destroying the timeline--and try not to destroy it herself in the process.

Actions Past by dutchbuffy2305
Sunnydale, 1997. Buffy makes a wish, with consequences...Buffy from the past and Buffy from the future will have to square their destinies and their lovers.

Her Way by dreamweaver sequel Changes
After Spike burns up in the Hellmouth, Buffy demands that the Oracles send her back in time.

His Way by dreamweaver
Spike finds himself resurrected yet again and sent back in time by the PTB to fix things for Buffy.

To Trick a Witch by Megan
Buffy finds herself caught in a world of witches that have it in for her. On the brink of a nasty spell, a stranger comes crashing into her world. Will he avert disaster, or ensure Buffy gets what is coming to her as the Slayer?

What You Wished For by pfeifferpack
Pretty much AU all the way, for obvious reasons. Starts in S4 at the beginning of "Goodbye, Iowa" then takes a quick turn to S1. Spike learns not only to be careful what you wish for, but also that when you swim in the Nile too long, you could drown.

Replacement by sus
After years of struggling for a life of her own, the immortal Slayer is finally free from the demands of her friends and the Council. Will she be willing to go back in time and do it all over again, just for the chance to be with the vampire that was always meant to be her other half? An enemy from the future will give her the chance, if she wants it.

I just remembered this one too. I didn't get on with it/finish it, but I think it fits the criteria...

In the Mind by WendyJane
When Buffy leaps from the tower at the end of her twentieth year of life, she expects nothing less than death. Peace. Instead she wakes up in a place where her friends believe her to be insane and a dangerous enemy wants her dead. How will she react when she finds out she wasn't the one who killed the Master? And everything she knows is a lie...

The first time travel fic I ever read was 'Somwhere I Have Never Travelled Gladly Beyond' by Strangefellows. The fanfic actually made me start to love time travel fics, which I previously hated

Despite being a WIP (and unfortunately, has not been updated since I last checked ), it's a quite great fic where Spike is sent back to BTVS season 1 after spending a bit of time in hell after closing the Hellmouth

I don't know if I've linked this properly, but click here for the fic

Summary: Realizing a little too late that they might have gotten the wrong Champion, the Powers That Be decide to give Spike a do-over, as it were. Replace him -- as he was when he sacrificed himself in the Hellmouth -- into the Slayer's story, right at the beginning, and let him do his job right. Of course, that's not going to be easy. But since when was anything easy in Sunnydale?