This dumps the documentation from an Open Peripheral device. I couldn't find one quickly so I wrote this. Improvements and formating changes welcome... (maybe an HTML dumper would look nice.)

doc_dump.lua

-- Dump open peripheral documentation to a file.

local args = {...}

if #args ~= 2 then
  print ("doc_dump <side> <file>")
  return
end

local perf = peripheral.wrap(args[1])
local data = perf.getAdvancedMethodsData()

local file = fs.open(args[2], "w")

local function p(s)
  --print(s)
  file.write(s .. "\n")
end

for method, details in pairs(data) do
  local argStr = "";
  for argi, argd in ipairs(details.args) do   
    argStr = argStr .. argd.name .. ", "
  end
  p(method .. "(" .. argStr:sub(1, -3) .. ") => " .. details.returnTypes)
  p("")
  p("  " .. details.description)
  p("")
  for argi, argd in ipairs(details.args) do   
    local opt = ""
    if argd.optional then
      opt = "(Optional) "
    end        
    p("  " .. argd.name .. "  (" .. argd.type .. ") " .. opt)
    p("    " .. argd.description)
    p("")
  end
end

file.close()