Don't tip it down your sink - it's illegal. You can be prosecuted under the Pollution of Watercourses Act (in theory, anyway). In general, I'd agree with other respondents who said use it up - sell and use by dates don't mean much anyway for a product of this sort. I go by smell, appearance and taste, as everyone used to before some nanny-ish quango decided we were all incapable of making even the smallest decisions about our own lives. As long as you've kept the oil reasonably cool it should be OK to use. Open it, tip a bit onto a spoon and taste it - you'll soon notice if it's rancid (which is probably the worst that can have happened). Other than that, if you decide not to eat it, your best bet is to take it to your local municipal tip for disposal - they usually have a cooking oil recycling section.
We dispose of our waste fat in a green cone in the garden (not a compost bin, this one digests food waste).