Lately I've only been playing an accoustic guitar after years of jamming with bands with my marshall half stack.  It's been pretty cool.  I've been playing a lot in the open G tuning.  That's from lowest string to highest: D, G, D, G, B, D. 

It's easy to go from standard tuning to open G.  First lower your low "E" string to D by sounding the E and D string together and matching the note (but of course a lower octave).  Then lower your "A" string to a G by sounding the A string and G string together lowering the A to match at the lower octave.  Then lower your high "E" string to D, again by matching using the sounding of the open D string.

When you play in this tuning, especially with a slide, you automatically sound like an old bluesman.  Or the Rolling Stones.  Keith Richards uses this tuning A LOT.  But he removes the lowest string from the guitar.

I really like this accoustic too, especially for the price I paid for it, which was only $80 on sale online at Musicians Friend.  It's an Epiphone AJ-1.  It plays and sounds great for the price.

One of my favorite songs in open G tuning is, Death Letter Blues, by Son House.  It's pretty easy to play.  He used a slide, but I just use my fingers on this one.