Should we put the references in slides/poster when we already have them in paper?
My rule for presentations is:


  Don't say anything that an interested member of the audience will not be able to remember.


This includes tables, but also bibliographic references to things that are not absolutely central to the presentation. There is a caveat: if the conference is recorded or the slides are available offline, you could write them in a non intrusive way (but not mention them during the talk).

Posters are different, as an interested reader may spend a longer time reading it. But then, the rule becomes:


  Don't include anything that an interested reader will not be able to remember, or won't bother to write down.


This trims away "previous work" (except, perhaps, a single very good review) or citations for the exact value of a certain constant you used; but you should include things that are indeed central.

And of course, by all means, you should include the reference to your own paper, so it is easy to find.