Well, the first guy to go to for iconic, entertaining Blues, is B.B King, but then you probably knew that.

You can't buy a "Best of the Blues" compilation without some tracks by him on it.
Now that I mention it, blues compilations are great resources. They're ubiquitous and cheap. Pick a couple up while you're standing in line at at gas station and you're bound to find something to love and explore further.
One of my favourite underrated bluesmen, is Bobby Bland. He's got a smooth falsetto voice that's full of emotion, and a clear sound that doesn't hide anything. His version of the classic "Stormy Monday" is my absolute favourite.
For a warm, acoustic take, check out Sonny Terry and Brownie Mcgee. They're a very playful and jovial duo, who'll pull you right down south and make you forget your cares.
There was some great crossover in the 70's between Rock and Blues. Led Zepplin, the Stones, Cream, the Allman Bros.... All these bands put there own powerful spins on old blues standards. You'd be surprised how many of their
greatest hits can be traced to a few blues artists.
Remember Layla, by Derek and the Dominoes? If you like Rock fuelled blues, I highly recommend picking up their album:
Layla and Other Assorted Love Songs You can't go wrong with Eric Clapton and Duane Allman weaving and battling with their unique guitar styles over Jim Gordan's piano. There are some scorching blues covers on that album.
Key to the Highway is my favourite.
In a similar vein, check out
Jimi Hendrix: Blues. What can I say; it's Jimi.
Now, I'm going to recommend a movie here, that you may scoff at: Crossroads starring Ralph Maccio. Seriously! Watching it, it's hard not to think
Karate Kid Meets The Blues, but it's good clean fun. The excellent sountrack was scored by Ry Cooder, the thinking man's bluesman. As you may know, The Buena Vista Social Club was his baby. Anyways, why not track down a copy and Join the Karate kid on his journey down into the deep South, looking for the lost blues of Willie Brown. Steve Vai as the Devil playing for Ralph's soul is a bonus.

Pick up a copy of the soundtrack afterwards.