check out my response in this thread: http://www.bikeforums.net/showthread.php?t=175157

For what you've described, the Giant FCR, Raleigh Passage, Trek FX or Marin Novato would be good bikes for you. They all allow the addition of fenders, racks, lights, etc. for commuting. They have low enough gears to climb anything and road wheels and tires for good speed. Gary Fisher makes a number of street/urban/commuter bikes that tend to be beefier than their Trek counterparts(Trek owns Fisher). They have wider wheels and tires.

Fisher Artemis


Trek 7.2FX WSD (Women's specific design)


The Trek will be a bit faster due to the larger wheels, skinnier tires, and slightly higher gearing. The Fisher will be more comfy due to the wider tires. Either one will handle your size. The Trek WSD bikes have smaller brake handles and the distance between the saddle and the handlebars is shorter because women have shorter torsos and arms than men and their hands are a bit smaller. Other companies such as Cannondale and Specialized make female specific bikes, too.

Note: many bikes are not designed for you to be able to put your feet on the ground while seated. If that's important to you, then consider bikes such as the Trek Sole Ride. It's a hybrid but you ride lower to the ground and can put your feet on the ground without leaving the saddle. You can lower the saddle on other bikes to let you touch the ground but then your legs are too cramped for efficient pedalling. People still do this all the time but for long term riding enjoyment it is not recommended.