The Collaborative International Dictionary of English v.0.48:

Attender \At*tend"er\, n.
   One who, or that which, attends.
   [1913 Webster]

WordNet (r) 3.0 (2006):

attender
    n 1: someone who listens attentively [syn: hearer, listener,
         auditor, attender]
    2: someone who waits on or tends to or attends to the needs of
       another [syn: attendant, attender, tender]
    3: a person who is present and participates in a meeting; "he
       was a regular attender at department meetings"; "the
       gathering satisfied both organizers and attendees" [syn:
       attendant, attender, attendee, meeter]