This site contains a selection of letters by Pliny the Younger, which I used in teaching Latin 301 (The World of Pliny the Younger) at Bates College in Maine.
A Brief Summary of All the Letters on this Site.
An Index Arranged by Topic with Links to All the Letters on this Site.
An Index Arranged by Book and Letter Number to All the Letters on this Site.
The rest of the site has the text of the Letters in Latin and translations into rather archaic English. They are from the 1915 Loeb edition, which is in the public domain.