Circus is my favorite Britney Spears album. Most of the tracks are easy to listen to and it has a lot of fun pop tracks (I'm not as fond of Britney's ballads because they are often really cheesy and her voice just works better on dance tracks).
My favorite songs on this album are: "Circus", "Womanizer", "If U Seek Amy", "Radar", "Blur", "Shattered Glass" and "Lace and Leather".
There is one good ballad on the album called "My Baby". While it is a little cheesy and doesn't really fit with the overall tone of the other songs, this one works for me. It's a pretty song about a mother's love for her newborn.
The dance-pop tracks are: "Womanizer", "Circus, "Kill the Lights", "If U Seek Amy", "Mmm Papi", "Mannequin" and "Radar".
The studio did a good job in picking the best tracks for radio release. "Womanizer", "Circus", and "If You Seek Amy" really are good songs and easy to dance to. If you own these and are looking for something else to try out, I'd recommend "Radar" for a fast, dance song and "Blur" for something medium-tempo. "Mannequin" and "Mmm Papi" are fun but mindless.
"Kill the Lights" has an edgier sound (but is another mindless track without much in terms of lyrics) and "Lace and Leather" is a medium tempo track with great guitar beats, but it's on the kinky side.
Overall, Circus is a fun album with lots of good songs to choose from. It's not one of those albums where you have to skip over half of the songs to get to the good ones.