Iv seen alot of request on the forums this, and a m8 of mine just asked for one, so here is one. its got a !add/!remove channel , so if u dont want it to join certan channels just add them :)

on *:TEXT:!idle*:#CHANNEL:{ 
if ($2 iswm $gettok(%banned.channels, $2, 32)) {
msg $chan Cant Join ( $2 _ , Banned )
halt
}
  if ($left($2,1) == $chr(35)) { 
    if ($me !ison $2) { 
      .join $2  
      .timer 1 2 check $2 $nick $chan 
    } 
    else { .msg $chan I'm already in $+(',$3,'.) 
    } 
  } 
  else { .msg $chan Correct syntax: !idle <#ChannelName> 
  } 
} 
alias check { 
  if ($me ison $1) {  
    if ($2 isop $1) {  
      writeini -n idler.ini $3 $2 $1 
    } 
    else { msg $1 Request failed. $+(',$2,') You dont have +o. try later if u got ops! 
      part $1 Error 
    } 
  } 
} 

on *:PART:#CHANNEL: { 
  if ($readini(idler.ini,$chan,$nick) != $null) { 
    part $readini(idler.ini,$chan,$nick) $nick has left $chan 
    msg $chan Purged $readini(idler.ini,$chan,$nick) 
    remini idler.ini $chan $nick  
  } 
}

on 1:TEXT:!Add*:#CHANNEL:{
if ($nick isop $chan) {
set %banned.channels $addtok(%banned.channels, $2, 32)
msg $chan $2 Is Now On My Banned List.
halt
}
}

on 1:TEXT:!remove*:#CHANNEL:{
if ($nick isop $chan) {
set %banned.channels $remtok(%banned.channels, $2, 32)
msg $chan I can now join $2
halt
}
}