there are so many options kanuski.
If you are looking for something new then a flash like the vivitar 285HV would serve you well. That plus a cheap optical slave or even cheaper, a cord, would give you an off camera capability.
If you want to use the wireless lighting systems of Nikon or Canon (with some cameras), in conjunction with a third party flash, then the Sigma flash would serve you well:
Sigma - Flashes
Regards,
Peter