More Latin Reading links

Scott and Horn's Latin Book One is on line and has macrons marked. This text
published in 1936 stands in a line of Latin texts including the later
editions under the title Using Latin from Scott Foresman. This book is
widely available through used book sellers at very reasonable prices. It is
also posted on-line at the Yahoo Group

http://groups.yahoo.com/group/Latinbk1/

This site requires that the users join (in order to discourage spammers).
This membership is entirely free. The Files section contains PDF files of
all the lessons along with Answers from two different sources. There are
some audio files to help students learn pronunciation and links to a number
of other Latin resources.

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Try looking in google books, if you are in the U.S.  Many of the
textbooks from the late 19th and early 20th century, which are now in
the public domain, have vowel lengths marked.  These are all PDF files:

Ritchie's "Fabulae Faciles" (Kirtland) <http://tinyurl.com/ltuqo4>

Lhommond, "Viri Inlustres," selections (D'Ooge) <http://tinyurl.com/lut8fv>
;

Cornelius Nepos, selections (Rolfe) <http://tinyurl.com/l37qqj>

Caesar, Gallic Wars (Allen & Greenough) <http://tinyurl.com/m42qwg>

Cicero, selected orations and letters (Allen & Greenough)
<http://tinyurl.com/kqga8m>

Livy, selections (Rolfe) <http://tinyurl.com/mewmhr>

"Readers" with selections from Latin authors, also sometimes have the
quantities marked.  You can find some of these in google books as well.

Many of the texts at <www.textkitcom>, also PDF files, have quantities
marked.