Items cyclists like me use and why:
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For sweat:
1.Jersey
 Of course the best way to deal with sweat is to remain
 at a decent weight. The more you are overweight, usually 
 means the more you sweat because you have to pull more 
 weight and your body has to work harder and cool off more.
 Jerseys are very expensive though. Be forewarned.
2.cycling caps
 Cycling caps are those funny caps worn by Tour de France 
 racers. They are really cheap; $8. They do wonders to keep
 sweat from rolling all over your face
3.Wash cloth
 Always carry a wash cloth when you ride. You might need
 to wipe stuff off yourself.

Others
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4.sandals
A.I use sandals because they are lightweight and I don't
 want to walk around in clipless cleats after a bike ride
 because they will scuff.
 When I ride a short distance in the city, I simply use
 an old bicycle inner tube to tie my sandals behind my seat
 on my seat post. The inner tube loops through the sandal
 straps and my seat post.
B.When I am not carrying cargo, I dont use a messenger bag.
 I keep my sandals tied to my seatpost and my chain around
 my waste. I found my lock at an industrial wholesaler in
 Baton Rouge. The catch-22 about getting a chain is you
 can't really get one because that would mean the supplier
 would have to cut the right length for you. If he can cut 
 the chain, then its no good to lock up a bike.
 I luckily found a chain that was 80 grade and exactly 3ft 
 long, perfect for my waist. On top of that it was the last 
 of the type, so the manager gave me an otherwise expensive 
 chain for free.
 I then pulled the chain through an inner tube (28cc) with
 the help of some olive oil to protect my bike from metal to 
 metal knicks.
5.messenger bag
 Okay, so they have been hijacked by non-cyclists as a 
 fashion item. Maybe that keeps the price down, so I 
 can't really hate them.
 Anyway messenger bags are good for carrying books, papers,
 yogurt, bread, and the like.

6.Helmet
 Where a helmet. People in Europe might not wear them, but
 that's them. I have not found a reason not to  waer a helmet,
 although I have heard weak excuses
 "I have nowhere to keep it when I park my bike."
 A:Loop your chain through the helmet straps, Thieves do not 
 steal helmets, nor do they wear them.
 "It makes my head too hot"
 A:Cheap helmets do in fact make heads hot. You need to purchase
 a helmet with plenty of ventillation or it will be a heat box.
 Good helmets cost about $80 retail.
7.Lights
 You always hear, "use lights, use lights!" Well not really.
 Incandescent lights are pitiful in regards to the battery life.
 THe battery life for incandescents is around 3 weeks of riding.
 Use LEDs which use less energy and have a longer battery life.  
 They should be available on ebay. Also get a flashlight holder  
 for bikes if you can find one.  Blinkers are cheap and are 
 available at WalMart. Get an LED  blinker. Mine last for about 
 6 months on 2 AA's.
 Beware that you are at a danger riding at night since
 motorists cannot correctly judge your speed since you only
 have a single headlight. 

  Have fun!