Is there a way to put addrfrom and addrto on the same vertical height when one of them is left-justified and another is aligned to the right? This is basically the layout I'm trying to achieve:

--------------------------

...

[\greetto]
[...msg...]
--------------------------
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You can use the \addrto macro to manually place both addresses using \parboxes:

\nameto{George Bush}
\namefrom{Paul Thompson}

\newlength\lento
\newlength\lenfrom
\setlength\lento{2in}% width of the box for \addrto
\setlength\lenfrom{2in}% width of the box for \addrfrom

\addrto{\parbox[t]{\lento}{The White House \\ Washington, DC}%
\hspace{\dimexpr\textwidth-\lento-\lenfrom}%
\parbox[t]{\lenfrom}{\raggedleft The Pink House in Avon \\ Belleville, IL}}

\greetto{Dear Mr. Bush,}

\begin{document}

\closeline{Sincerely yours,}

\begin{newlfm}
How are the azaleas?
\end{newlfm}

\end{document}

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Thanks! And pardon me for the huge delay. I couldn't figure out the letrinfo.tex error and thought that my texlive installation was broken. \o/ –  plaes Sep 20 '11 at 9:03
In order to suppress some of the whitespace it is possible to add \vspace{-1cm} inside the \addrto. –  Rovanion Jul 16 '13 at 12:20