I waited a while on the last two, as the higher up you go, the more obvious the choices tend to be. However, the final two haven't budged in my mind, and are firmly entrenched as essentials in my iPod. So here goes, the final two.
Al Green: "Driving Wheel" ("Can't Get Next To You" CD): This song comes from one of the great R&B records of all time. It also featured the immortal version of "Can't Get Next To You," which was the way most blues bands performed the song (as opposed to the Temptations' hit version), and "Tired Of Being Alone." What the set also featured was some of the greasiest, down home funk Memphis ever produced, by one of it's legendary bands, the Hi-Rhythm section. If you're in any kind of car, the cool but intense opening riff of "Driving Wheel" just fits right into the flow and draws you into one of the coolest laid back funk blues of all time. This song is immortal, but so is the whole album. Treat yourself to the whole dinner, and don't just download the one song.
Caddy Rating: Safe for all speeds, and a sure cure for the boredom of any long commute.
Booker T & The MGs: "Green Onions:" There's been thousands of great car songs (and songs that sound good in a car) but none are on the same level as this one. A one off jam based on a standard blues progression, that the label President didn't want to release because it sounded so simple, it creates a musical groove so perfect that even the group could never reproduce it live. A rare cut that is laid back, but also smolders with the blues. A car song so perfect that even in the movie "American Graffiti," it was used in the final drag racing scene even though it wasn't period-accurate. I almost picked another favorite, Freddie King's "The Stumble," but decided that in the case of Green Onions, being the obvious choice was too obvious to ignore.
Caddy Speed Rating: Perfect at any speed, even if stopped (in which case, add hamburgers and fries for the perfect mood).
Coming Soon: Talking about the blues and the digital age, and since it was so fun, another blues list of some sort.