I recommend Lavazza Gran Filtro coffee. It's Italy's #1 coffee and has good flavor and is very, very smooth. You can find it at
http://www.amazon.com/ They make a lot of espresso blends, but if you're intro drip coffee then Gran Filtro is the best they make. There is a dark roast too, but I think the original roast tastes best.
If you don't want to spend that much on coffee, Tim Horton's (rated 5 stars) is also listed on amazon and is very cheap.
Now at the grocery store I just switch between Dunkin' Donuts (all-american), Starbucks Sumatra (earthy, herbal), and Starbucks Veranda Blonde (smooth, mild).