I'm working on the Bobbsey Twins books. Only the first 15 books in the series are in the public domain; 13 of the 15 are available at Project Gutenberg.
- The Bobbsey Twins, or Merry Days Indoors and Out, 1904
- The Bobbsey Twins in the Country, 1907
- The Bobbsey Twins at the Seashore, 1907
- The Bobbsey Twins at School, 1913
- The Bobbsey Twins at Snow Lodge, 1913
- The Bobbsey Twins on a Houseboat, 1915
- The Bobbsey Twins at Meadow Brook, 1915
- The Bobbsey Twins at Home, 1916
- The Bobbsey Twins in a Great City, 1917
- The Bobbsey Twins on Blueberry Island, 1917
- The Bobbsey Twins on the Deep Blue Sea*, 1918
- The Bobbsey Twins in Washington, 1919
- The Bobbsey Twins in the Great West, 1920
- The Bobbsey Twins at Cedar Camp**, 1921
- The Bobbsey Twins at the County Fair, 1922
* The Bobbsey Twins on the Deep Blue Sea -- not on Project Gutenberg, but found at books.google.com
** The Bobbsey Twins at Cedar Camp -- not on Project Gutenberg; still looking for a copy.
I'll get the versions from Project Gutenberg converted to the various eBook formats first, then work on a transcription of the Deep Blue Sea episode.
EDIT: I successfully bought a copy of The Bobbsey Twins at Cedar Camp from somone on eBay. I guess I'll be figuring out how to scan and OCR a book.