A selected Cello and Guitar duet by J.Bergmiller (19th century).

With Guitar standard notation and tablature (separate parts with tablature and standard notation). 
With downloadable mp3 for audio help (both Cello and guitar, guitar only, guitar and cello with reduced volume. for practicing the Cello).

Total seven pages (3 pages both Cello and guitar, 1 page Cello part, 2 pages guitar with tablature part, 1 page guitar without tablature part), 3:20' min - Early Intermediate.

Il Fuggitivo from op. 8-3 by Joseph Joachim Raff (May 1822 - June 1882).

For Guitar Duet (Classical or Acoustic fingerstyle).

With finger position suggestions. 
Early intermediate, 0:55' min.
Pages : 4 pages (Both Guitars 2pages, I Guitar 1 page, II Guitar 1 page)

Duo de la Molinara, from the opera L'amor Contrastato (1788) by Giovanni Paisiello (9 May 1740 5 June 1816).

Guitar Duet. Early Intermediate to Intermediate.

Pages: Four (4) pages (2 pages both guitars, 1 page guitar I, 1 page guitar II),1:10' min.

Mauro Giuseppe Sergio Pantaleo Giuliani (27 July 1781 8 May 1829) was an Italian guitarist, cellist, singer, and composer. He was a leading guitar virtuoso of the early 19th century.
This is the fifth of the set of 16 easy and pleasant duets for flute and guitar composed by Mauro Giulani at 1810.
For Flute and guitar duet.
With downloadable mp3's for audio help (with both the Flute and guitar and one with guitar only for practicing the Flute).  With guitar tablature.
Pages: Six pages (2 pages both Flute and guitar, 1 pages Flute part, 1 page guitar part, 2 pages guitar with guitar tablature part)., 2:30'min.

Hark! The Herald Angels Sing is a Christmas carol that first appeared in 1739. It features lyrical contributions from Charles Wesley and George Whitefield, with music adapted from by Felix Mendelssohn's "Vaterland, in deinen Gauen" by William H. Cummings.

For Flute and Guitar duet.

With standard notation and tablature.
With Lyrics.
Easy to early intermediate.
With downloadable mp3 for audio help.

Pages: Four (4) pages, (3 pages Melody/Flute and Guitar with tab, 1 page Melody/Flute part).