Most homebrew batches are 5 gallons of beer. However for a long time now I have been doing smaller batches like one, two and three gallon batches. I've really come to like the three gallon batches. They fit in a 5 gallon carboy with no blow off of overflow. They are about 30 bottles so just right for having some to share/trade but enough to have some of your own. As you might guess, I still bottle. So bottling 30 bottles saves some time. Also I just did two 3 gallon batches at once. I find that I can brew more often yet get a good amount of beer still. It also saves a bit.
To accomplish this I use hopville.com for formulating and scaling recipes. I keep the percentages and OG, IBU and stats as close as I can. Sometimes its hard to keep SRM the same as some quantities do not split nicely. Hopeville.com does not do grams either so sometimes the spec'd recipe is a bit off from brewday. Overall I have had great success in small batches. You do have to watch the pitching rate but 3 gallons for a smack pack or vial is a good amount.
I'm also looking a making a 2 liter bottle keg.