The subject has been covered way more times than suggested. one fellow just the other day, was only able to remove his after over a year trying on and off, I guess he finally had his lucky day. He'd not found the special solution either.
Sheldon Brown writes about this and I'd tried in the past before having read it. At the time, I'd made the choice to sacfrice the saddle by wrecking it. The saddle that was on the bike was pretty good, since then I've used cheap ones. Wrestling the post out using the saddle as a handle. What better to to use as a wrench. A saddle grabs the post entirely. If it's a modern post, the saddle will be sufficiantly flexable overal for added pressure (dif. to articulate) like a torque lever along with leverage. If it's an old type bare-tube post with the saddle clamp clamped to it, I can't think of a better task specific tool either.
Try a special Liquid Wrench type product PB Blaster is the best that I've come across, parts stores have it. Let it sit some. If nothing helps, last resort is to drip some Coka Cola down in there, an old exh. man. stud. rem. trick.