Here is a solution using a csv data file with the names, then using the datatool package to create the invitations, finally using Werner's recommandation to use a pdf printer to get 4up. I used PDF995 (which was on my laptop).
First create the csv file. I just used notepad to create the file and then did a save as to marie-names.txt
I now have the following file in csv format
FirstName
Bob the Tomatoe
Larry the Cucumber
Big Bird
Waldo (if found)
Now I modified the instructions found at http://latex-my.blogspot.com/2012/01/mail-merge-batch-generating-documents.html to get the following MWE. Note: old-border.jpg is from http://www.fromoldbooks.org/Aubrey-HistoryOfEngland-Vol2/pages/438-Border-of-twigs/ and picture1.png was converted using powerpoint from http://aknockoutphoto.wordpress.com.
% Use scrartcl to allow larger base font size
\documentclass[16pt]{scrartcl}
\usepackage[left=3cm,right=3cm,top=6cm,bottom=5cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage{wallpaper} % For background image frame
\usepackage{datatool}
% Load database 'names' from file 'marie-names.txt''
\DTLloaddb{firstnames}{marie-names.txt}%Import the txt file in csv format as a database
\begin{document}
\linespread{2}\selectfont %Changing linespacing for the font and enabling the change
\pagestyle{empty}% Turn of page numbers
% Set old-border.jpg as background image
\TileWallPaper{\paperwidth}{\paperheight}{old-border}%Loading a borderpattern
% Ref: http://www.fromoldbooks.org/Aubrey-HistoryOfEngland-Vol2/pages/438-Border-of-twigs/
% For each record (line) in database 'names'
% Assign field values by name to macros
\DTLforeach{firstnames}{\name=FirstName}{
{\centering
{\LARGE\bfseries Birthday Party Invitation}\par
\smallskip\large Dear \name,\par\smallskip
You are invited to a cookout to celebrate Cookie Monster's 44th birthday!\par
\medskip
Saturday, November 10, 2012 from 5:30 -- 9:00 p.m.\par
\medskip
1234 Sesame Street\par
Anywhere, USA\par
\medskip
Please RSVP to Miss Piggy at 987-654-abcd\par \bigskip
\includegraphics{picture1.png}\par
\pagebreak}
}
\end{document}
Now compile with pdflatex and view. Now print with a package capable of creating a 4up pdf page and your get

\invite{<name>}would permit to create the desired invitations by using one\invitecall per guest without an explicit list. – Christian Lindig Jun 26 '12 at 12:17