In my (CT) game, I use all them often.
I don't tie a skill to a single attribute. Instead, I pick an appropriate stat to govern a skill check.
For example, DEX governs AutoPistol most of the time. But, if the character were at an open market bazaar on some low-law world, looking at a table of AutoPistols to purchase, I'd use AutoPistol governed by EDU fo the character to pick quality weapons from the trash.
Let's say the particular weapon the player purchased had a well concealed, tiny, secret compartment in the handle. I'd have the character throw an AutoPistol task governed by INT to find it as he cleaned his new pistol. Or, I might have the character throw AutoPistol governed by SOC to recognize that that particular pistol is used exclusively by the local lord's elite guards. Etc.
DEX - Used for firing weapons in Fire Combat.
STR - Used for HTH or Melee weapons in Brawling Combat.
END - Used to determine how many actions a character is allowed every round.
INT - Used in determining initiative and any time the character needs to figure a puzzle type problem...or even if the character notices something that he might not (a perception roll). Also used for "determination" type rolls.
EDU - Used whenever a character's learned knowledge is important--what he knows about a particular subject. EDU is a measure of how well the character can apply his learned knowledge (not correspondent to a particular level of education in the manner of SOC and the character's actual social standing). No skill can be higher than a character's EDU. And, EDU is used for tasks concerning skill improvement.
SOC - Used for all sorts of inter-personal tasks--even NPC reaction throws. Used in character generation for checks. Unlike EDU, SOC is a measure of the level of the character's social standing--each level of SOC corresponds with a level of social standing (whereas a character with high EDU may not have finished high school but is self-taught and has the ability to apply his learned knowledge well).