Time to update.
Starting dates for the summer:
Burn Notice: season premiere June 3rd (USA Network)
Royal Pains: season premiere June 3rd (USA Network)
Lie To Me returns on June 7th (FOX)
Persons Unknown premieres June 7th (NBC)
Pretty Little Liars premieres June 8th (ABC Family)
True Blood season premiere June 13th (HBO)
Scoundrels premieres June 20th (ABC)
The Gates premieres June 20th on ABC (Rhona Mitra everybody!

)
Leverage returns with it's third season on June 20th (TNT)
Hawthorne: season premiere on June 22nd (TNT)
Memphis Beat premieres June 22nd (TNT)
Rookie Blue premieres June 24th (ABC)
Hung returns with it's second season June 27th (HBO)
Futurama finally returns on June 24th (Comedy Central)
Entourage: new season premieres June 27th (HBO)
Huge: premieres June 28th (ABC Family)
Louie: premieres June 29th (FX)
Rescue Me: final season starts on June 29th (FX)
Warehouse 13: second season premieres on 06. July 6th (SyFy) (some sources however say that the season premiere will be pushed back a week)
Haven premieres on July 9th (SyFy)
Eureka returns on July 9th (SyFy)
The Closer: season six starts on July 12th (TNT)
Rizzoli & Isles will premiere on the same day (July 12th) on TNT
The Glades: premieres July 13th (A&E)
Covert Affairs: premieres July 13th (USA Network)
White Collar: second season premieres on July 13th (USA Network)
Psych: new season premieres July 14th (USA Network)
Mad Men: new season premieres July 25th (AMC)
My Boys season 4 returns on TBS on July 25th
Rubicon: new AMC series, starts August 1st
Weeds returns with a new season on August 16th (Showtime)
The C Word premieres on the same day (August 16th, Showtime)
Melissa & Joey will premiere on August 17th (ABC Family)
Dark Blue will return somewhen in August (TNT)
Sons of Anarchy is scheduled to return with season 3 on September 1st (FX)
Caprica: second half of the 1st season will start September 17th (SyFy)
Dexter is scheduled to return on September 26th (Showtime)
As most broadcasters/networks have introduced their new tv schedule for the next year, here's a list of new/cancelled/returning shows:
ABC
cancelled/ended: Better off Ted, Eastwick, FlashForward, Hank, Happy Town, Lost, Romantically Challenged, Scrubs, The Deep End, The Forgotten, Ugly Betty
returning next season: Brothers & Sisters, Castle, Cougar Town, Desperate Housewives, Grey's Anatomy, Modern Family, Private Practice, The Middle, V
new shows: Better Together, Body of Proof, Detroit 1-8-7, Happy Endings, Mr. Sunshine, My Generation, No Ordinary Family, Off The Map, The Whole Truth
FOX
cancelled/ended: 24, Brothers, Dollhouse, Past Life, Til Death
returning next season: American Dad, Bones, Family Guy, Fringe, Glee, House, Human Target, Lie to Me, The Cleveland Show, The Simpsons
new shows: Bob's Burgers, Lonestar, Mixed Signals, Raising Hope (from the creators of My Name Is Earl), Ride-Along, Terra Nova, Running Wilde
The CW
cancelled/ended: Melrose Place, The Beautiful Life: TBL
returning next season: 90210, Gossip Girl, Life Unexpected, One Tree Hill, Smallville, Supernatural, The Vampire Diaries
new shows: Hellcats, Nikita (with Maggie Q!)
NBC
cancelled/ended: Heroes, Law & Order, Mercy, Trauma
returning next season: 30 Rock, Chuck, Community, Friday Night Lights, Law & Order: Special Victims Unit, Parenthood, Parks and Recreation, The Office
new shows: Chase, Friends with Benefits, Harry's Law, Law & Order: Los Angeles“, Love Bites, The Paul Reiser Show, Outlaw, Outsourced, Perfect Couples, The Cape, The Event, Undercovers
CBS
cancelled/ended: Accidentally on Purpose, Cold Case, Gary Unmarried, Ghost Whisperer, Miami Medical, Numb3rs, The New Adventures of Old Christine, Three Rivers
returning next season: Criminal Minds, CSI: Crime Scene Investigation, CSI: Miami, CSI: New York, How I Met Your Mother, Medium, NCIS, NCIS: Los Angeles, Rules Of Engagement, The Big Bang Theory, The Good Wife, The Mentalist, Two And A Half Men
new shows: Bleep My Dad Says, Blue Bloods, The Defenders, Hawaii Five-O (Trailer looks amazing), Mike and Molly, yet untiteled Criminal Minds spin-off
HBO
cancelled/ended:
returning: Bored To Death, How To Make It In America
new shows: Boardwalk Empire, Game of Thrones
TNT
cancelled/ended:
returning: Burn Notice (season 5 ordered before season 4 even started), Men of a Certain Age, Southland
new shows: Franklin & Bash
Furthermore:
Starz will produce a prequel to its new show "Spartacus: Blood and Sand" and orderer a second season of Spartacus. On top of that Starz ordered a full first season of a show called "Camelot" based on... well, you guess.
HBO is planning a show called "Luck" based on horse-betting starring Dustin Hoffmann and Nick Nolte, a show about an infamous Hollywood-blogger starring Diane Keaton and Ellen Page and a show about a heart surgeon played by Kevin Kline who murdered his mistress. And HBO announced that Eastbound & Down will get a second season.
Showtime renewed Californication. Casting for the new season has already started. Nurse Jackie and Untited States of Tara have already been given a third season.
Edit: Ehm, ok, I don't know, why half of my posting was already there, when I posted this final version. Maybe I accidentally hit the reply instead of the preview button once. So, this posting (the second one) is the complete info.