There is not much difference at all. Both mean the same thing: you started working here at some point in the past, you continued to work here up to the present moment, and you may or may not continue to work here (neither phrase implies that you have stopped, or are about to stop).
All of the followings sentences are possible:
"I have worked here since 1980, and I shall continue to work here for many more years."
"I have been working here since 1980, and I shall continue to work here for many more years."
"I have worked here since 1980, but now I am leaving."
"I have been working here since 1980, but now I am leaving."