couple of super sleepers:
shad meier, NO - he could become the starter if boo doesnt get his act together. he's got decent receiving skills.
george wrighster, JAX - like meier, came into the league as more of a receiving TE, showed some decent skills before getting hurt last year.
desmond clark, CHI - he and grossman hooked for a couple of 25+ yarders before rex went down. clark has been a decent producer at TE before.
I also think if one of aaron shea and steve heiden emerge as the clear starter in cleveland, they will be a serviceable fantasy TE - they caught 9 TDs between them last year.
but to answer the original question, THE sleeper TE of 2005 will be ALEX SMITH. He will defy the "rookie TEs dont do much" rule. I believe that Gruden drafted him with visions of smith slicing defenses right up the seams with his ability to stretch the field and use his size/athleticism to create mismatches whether a DB or LB is covering him. Smith also has the best frame to be the go-to guy in the red zone for the bucs. It would not surprise me at all to see smith emerge as the #2 option in the tampa passing game this year - he has WR like skills at TE.