I was in creative mode and I killed the ender dragon. I then broke every portal block so I could collect the dragon egg. I forgot I could cover them, and now I can't escape the end without dieing. Can I create another portal home?
Short answer: NO.
Once you break your portal blocks, there's no going back, unless you spawn another enderdragon (to spawn a portal upon death), place the necessary blocks yourself (via TMI (aka Too Many Items)), but no other solutions. Note, nether portals also do not work here, as they cannot take you back as well.
Unless you plan to use external 3rd party programs, as fredley mentioned, you cannot create a portal home.