Please support the creators of works that you enjoy (purchase links are on the project pages). And then after that... toss a coin to your scanlator, if you'd like. There aren't special privileges or anything for donating— the only reward is my appreciation and possibly faster releases in general. I'm considering purchasing a drawing tablet now, which would let me do manual redraws faster.
Anyway, I do spend quite a bit of time and effort on these projects, so if you choose to donate, you have my sincere thanks!