Some EXCELLENT Advice and VERY NICE bikes posted in this thread already.
Starting out cycling it depends on how hands on you want to be. Do you want to get into it hardcore? decent kit, decent bikes, decent rides? Or do you want to do it more casually? Ride to the shops? Bike path loops etc??? Do your own maintenance?
It all depends on what sort of riding you do.
I myself do around 200-220km a week on a track bike on the street.
Last saturday I rode Perth - Mandurah with a couple of mates, 110 kays in one hit, fixed gear. 32kph average speed. Not bad for a single gear bike (52/16 gear ratio with headwind) and not having done a longer ride like that in a few months. Especially when I'm only doing around 20-30km a day in the arvo's after work.
If you want an easy to use, easy to maintain bike, get a single speed. No gears to worry about, reasonably cheap to get yourself in and a great urban commuter.
If Bike Messengers swear by Single Speeds & Fixed Gears (track bikes) then average joe will do ok.
One thing I do not reccommend is riding fixed straight out - especially brakeless.
Ive built a few track bikes over the last 12 months and all cost a varying amount, from as little as 350 to up over 1500 - which is decent coin on a bike with 1 gear and no brakes lol.
anyway, pic for reference.
Anyway, a lot of these guys have given better advice than me, especially in regards to road training... I can cover off on the more urban/social end of things.
Especially because in a year or 2 my knees will blow out from riding a big ratio brakeless and will need surgery to ride/walk again HA HA