Actually, I almost prefer them when they're made ahead and reheated in the oven (in a single layer) because they get a bit crispier on the outside, which I like.

I sometimes make a huge batch and freeze a lot of them - they freeze well, and reheat straight from the freezer quite quickly. Comes in handy when doing mini ones for a cocktail party (topped with smoked salmon/trout or caviar or even just sour cream/creme fraiche and chives) - I get to 'be' at the party, instead of being a latke machine in the kitchen.

oh, or (and I agree this is not the *best* solution): make your cakes earlier in the day and then heat them up at mealtime. I recommend you lay a cooling rack on a sheet pan and then put the cakes on the rack. Heat at 375 for about 8-10 minutes until piping hot and sizzling.

Potatoes turn black when their starch is exposed to air. If you can't make them right away, as savorykitchen rightly suggests, cover the grated potatoes with water. Drain and wring them out well in a tea towel right before you make them.

Make them right away - make the batter/mixture and then start frying. I use as many skillets as I have burners and just start cooking. Using cooked potatoes can also solve the blackening problem.