At the moment I have a Diamondback Explorer, a Cobra Mk III, and Adder, an Eagle, lots of Sidewinders(for bookmarking purposes!) and recently sold a Hauler and Viper.
My current loadout which is designed for exploration and long distance missions(also handy for Powerplay) is as follows
Some defence in case I get into trouble, but with this ship I tend to run! Burst laser on large hard point and two Multi-cannons on medium hard points. Still need to get myself A class thrusters to be better able to outrun attackers after an inderdiction, as boost speed is not great with standard thrusters.. After the latest update 1.4.1 which makes avoiding inderdiction much harder, I tend to just submit right away and try and escape asap.
My main upgrades for this ship are the FSD with is A rated class 5. This give me a jump range of 29ly. If I ditched the shields, got rid of chaff launcher and point defence and lighter thrusters, it would take me to about 32ly jump range.
Advanced Discovery Scanner is expensive but worth it, also Detail Discovery Scanner for exploration(and yes I know I have it in a class 4 slot) - plan to swap with my Shield Generator
I have swapped out my cargo hold for a 16 capacity hold, so that I can do multiple long distance missions at once(many of these pay out handsomely - got 3.2 million credits for one mission the other day!)
If I was doing serious exploration way beyond inhabited space, I would possibly swap out the cargo rack for another fuel tank, upgrade my fuel scoop(essential for exploring)