If it looks like its coming form the oil filter, the oil cooler which is snadwhiched in between block and filter may be leaking. Otherwise oil leaks often are hard to find as the oil blows back during operation. Look for leaks just foward of where the oil is. The best thing to do is to clean the engine with degreaser or brake cleaner and run it at idle for a while and look for the leak on a clean engine. That way blow back will not mis-lead you.