We were going to use a wide topped glass but KD preferred a flat bowl thing, so we use a plastic tupperware type thing, about the size of one that would hold a sandwich. Works for him and it's very easy to get the goods from!
Glass is what is recommended, especially if there is going to be any lag time between filling it and inseminating it. Glass is easy to sanitize and doesn't leach chemicals. (Have you seen all those reports on common household chemicals being linked to infertility?! I just tossed my plastic tuperware and am going out to by glass containers to pack my lunches in!)
We used an old glass olive jar about the size Papa mentioned. It took a couple runs through the dishwasher to get it as clean feeling as I wanted it but after that it was fine. I got preg once while using that jar (but m/c'd). We don't use it now since our new KD is shipping from across the country.
The key thing is to make sure it is perfectly dry before handing it over. No drops of water from washing! Water can damage the sperm. I use to put the jar in the toaster oven before our donor came over to dry up any droplets. When he saw me pull it out of the oven to cool a bit he started cracking up! There were a lot of "one in the oven" jokes that night.