OK--stout, either dry (like Guinness) or sweet would be a great first beer. Beers with lighter flavors and colors can be a little trickier, because even small flaws are noticeable, but that's not really an issue with stouts.
If you have a LHBS, you could just pick up a dry stout or sweet stout kit there, or order from one of the big on-line retailers like morebeer.com, austin homebrew supply, northern brewer...Those places often have options on yeast: if you order liquid yeast (which tends to give the best results), be sure to get an icepack so that it has a chance to reach you in a viable stage. Depending on where you live, dry yeast might be a better choice for shipping in August.
As far as fermenting times, yes, some styles have longer fermentations (lagres had longer fermentations than ales, typically), but an even bigger factor is that some styles need more "cellaring" after fermentation before they reach their prime.
Lagers are a bit more complicated than ales to brew: so brewing something like Grolsch might need to wait a few batches.