Ashlee Simpson [ tickets ]'s upcoming release, "Bittersweet World," due April 22, features the single "Little Miss Obsessive," currently available at major digital retailers including iTunes, according to a press release. The single features guest vocals from Tom Higgenson of the Plain White T's.

Simpson has been crossing the country promoting her forthcoming album on radio shows, at Wal-Mart in-store appearances and at midnight club gigs. Simpson will appear March 29 on Nickelodeon's "Kids Choice Awards," April 18 on "The Today Show," April 21 on "The Tonight Show with Jay Leno," April 22 on "Dancing with the Stars, April 23 on "The Ellen DeGeneres Show," and April 24 on "Jimmy Kimmel Live." The pop singer then heads to Europe to continue her support of "Bittersweet World," which is Simpson's third album. Plans are in the works for a summer tour.