You can also find a huge number of free dishcloth patterns just by Googling "knit dishcloth pattern free" and see what comes up.
These dishcloths are a wonderful way to develop your knitting skills, escalating you to more and more expertise quickly.
Here's a hint: I found that using thick cotton yarn for these cloths made them too heavy, too slow to dry out and too prone to getting, uh, slick and slidey.
So I much prefer using moderately-heavy [size 10] crochet thread like used for doilies. This is thin enough to hold their scrubber-ability and it dries relatively quickly. And is surprisingly durable - I use mine for washcloths in our shower. But there is rather a high shrink-factor that needs to be taken into account when you make one.