The new review icon (which only appears when you have 500 reputation or more) looks like this:
or in context (ooh look a tooltip!)
it's been suggested that it looks kinda like a stapler... This icon may be getting changed soon, but it's going to be in the same place and it's not going to have any text saying "review" :(
When you click the button, you get a mini review queue dropdown-kinda menu
There are some dots next to the queues that have stuff to review in them. Different colours indicate how many items there are (at the time of taking this screenshot, the Close Votes queue has way more items than others, and the Reopen queue is empty, while each of the others has a few items). (The tools link in the mini menu takes you to the moderator tools page. If you have less than 10k reputation, you won't see this link.)
You can click the queues to go straight to a queue of your choice and start reviewing immediately, or you can see all the queues by clicking all queues.
Aaah! There they are :)
P.S. I guess it seems like once you've figured out where the review queues are then, problem solved... but SO users have reported that they find themselves reviewing less although they obviously know where the icon is. You might find that you have to remind yourself to review, since there isn't a word on the screen planting the idea of reviewing in your brain.