I'm pretty sure you can't force your opponent to play faster....
I think that if you are in a "winning" or "superior"position you may maybe consider to begin another game since this one is on a good way for you and you already know that you'll have to wait +10 days before each move.
I also usually take lots of time before playing my moves and love to take 3/4 looks at the board before playing.
I lost too many games because of quick play... maybe your opponent too 
What happened is that I clicked on a 15 days per move open seek,... Is there any way I can get him to play faster or at least resign?
Of course there is no way to force a player to resign, nor play faster than the designated time control.
This topic has been discussed so many times before. Generally the outcome is; it's unsporting, but since he is not breaking any rules...
Maybe send him a nicely written message. Most people respond to negative behaviour with negativity of their own. A polite request might do the trick. Can't do any harm.
if you resigned it inside 6 moves it wouldn't effect youre grading then don't play him again
Well I did send him a polite (if a bit annoyed) message, but of course he's ignoring me. I didn't know the topic had already been discussed a lot, sorry about that.
I only asked because there is a little message that appears when you take vacation time to tell you not to do it just to annoy your opponents when you're losing and I thought maybe it was the same kind of thing.
bigmac : he only started to REALLY stall once he began to lose, and began not to play anymore when the game was hopeless (around move 20). Oh well, I guess there is nothing to be done.
Hi everyone,
I'm playing a game at the moment which is pretty much won, but apparently my opponent has decided he's simply going to wait until I get bored and run out of time. What happened is that I clicked on a 15 days per move open seek, and that didn't bother me that much at the beginning (I like to take my time too and maybe he is away from home a lot or whatever); but now the guy is just not playing any more.
Basically all my moves are already played even before he moves each turn, but it still takes him the whole 15 days to do anything, even though his move is basically forced and he connects to the site every couple of days or more often.
Is this considered all right on this site? I don't care that much about the points and I don't think I'm going to forget about the game and timeout anyway, but I like to keep only a small number of games running at any time and this kind of tactic annoys me. Is there any way I can get him to play faster or at least resign?