My ride is 12 miles one way, and I also arrive as a sweaty mess. I do the same as some others and take a baby wipe bath and then change into work-appropriate attire. I do not have a locker or anywhere to store clothes, so I take everything with me on my rear rack.
I don't even try to wear non-cycling specific pants anymore. I've GOT to have the padding in the shorts. But I got a deal at Dick's Sporting Goods on some Nishiki 'liners,' so I can wear those under other pants. I'm not on a comfort bike of any kind. I'm on a road bike with a pretty hard saddle, so the extra padding is very necessary. I never leave without gloves either, just in case of spills, but the little bit of padding in there is nice too.
I got a couple neon yellow shirts at Wal-Mart (never thought that color would be cool again), and I wear those in the summer by themselves. I have a neon-yellow and reflective tape vest like you see on construction workers for lower-visibility days and days where I need to wear something warmer than a tee or tank. I don't bother with jerseys because I've got so much stuff to carry with me anyway, why not use the rack? It is a commute, not a race, so I'm not worried AS much about speed or wind resistance.