My personal favorite for commuting is a cyclocross bike. I use my 2013 CAADX for commuting, light touring, and it has been my bike for 3 triathlons.
It is more aggressive in geometry, aka racey, then the other type of bikes below, but thats more up to personal preference.

A few cyclocross bikes to look at in no order are:

-Cannondale CAADX
-Specialized Crux
-Jamis Renegade
-Trek Crossrip

All of these come in various trim packages that can run from about $1000 to $Car

Another kind of bike that may strike your fancy is what is referred to as a "Touring" or "Endurance" road bike. It tends to be a little more relaxed in its geometry, aka comfortable, but still gives you the versatility that you are looking for. With the adoption of disc brakes these bikes are able to handle wider tires for comfort, mounting for racks and fenders, and can still be use for more spirited riding. If you haven't riden a bike in a while it is a very good way to get back into cycling.

A few in no order are:

-Surley Straggler, Crosscheck, Long Haul Trucker (very popular, you will see a lot of these around the city, Captial Bikes, City Bikes, and a few others sell these)
-Trek 720 or 520
-Specialized Diverge

Honestly this list goes on and on.

I think the first thing to do is sit down and really figure out what it is you want to do with the bike. Once you have that the next step is to ride. Ride as many of that type of bike as you can. Once you find one that fits your needs and is comfortable you can then either find a trim package that fits your budget or look around online or in store for last years model of that bike (I saved $500 on mine doing this).

Another budget way is to check out Bikes Direct. They sell their own house brand bikes for all of the bike categories listed in this thread. Some may say they arent as nice, but I personally have friends who are doing their 5th year of riding on them.