"Online research" is supposed to be what lazy students do. Scholars, meanwhile, are expected to travel to different libraries, archives, and museums to consult documents, photographs, and books. This, however, is not necessarily true anymore because more and more resources are becoming available online. In some cases, surfing the web is not only less expensive, but also more productive because researchers can examine texts more closely and are not limited by policies regarding physical access to the materials. Plus, if your university library is closed, but you just need to check one small detail, online research is the most convenient alternative.
The 5 websites enumerated below in alphabetical order are, in my opinion, the best free sources for Filipiniana online at this time. They each have their own strengths and weaknesses, and you'll have to search them all if you want to make sure that a particular title is really not available on any of them, but what's really good about these sites, is that unlike others that only reproduce the texts, you can see for yourself how the text originally appeared on the page, you can cite specific page numbers as if you had the book in front of you, and you can even download the entire book or certain pages (with one exception, which is indicated below).
If you have any suggestions, please send a message or leave a comment via Facebook.
Biblioteca Digital Hispanica (Hispanic Digital Library)
This site is, of course, in Spanish, so if you can't read Spanish, make sure you click on "Welcome" (other languages aside from English are also available) at the top-right corner of the page. Once you're looking at the book, you can download the entire book by clicking on the disk icon on the upper-left corner of the page, next to the book's title. Some of the books available are:La música popular de Filipinas (Walls, 1892)
Archivo del bibliófilo filipino (Retana, 5 vols., 1895-1905)
Mga tala ng aking buhay at mga ulat ng Katipunan (de Jesus, 1932)
HathiTrust Digital Library
This website was very helpful when I was doing my PhD because it was the only one then that had such a huge collection of downloadable books on the Philippines. Note, however, that many titles are not accessible to all. You'll have to select "Full view only" to limit your search to the ones that are freely available. Also, if you see that a book is downloadable today, don't assume that it will be downloadable tomorrow. So it's probably best if you download a title when you see it. Some of the books I've downloaded in the past are:The Philippine Islands (Blair and Robertson, 55 vols., 1903-1909)
A history of the Philippines (Barrows, 1905)
A short history of the Philippines (Jernegan, 1905)
This site doesn't only host the Wayback Machine, it also provides access to a lot of books digitized by different libraries around the world. What's good about it is that you can actually turn the pages by clicking on the left or right pages. Some of the books available are:Arte de la lengua tagala (Totanes, 1745)
The medicinal plants of the Philippines (Pardo de Tavera, 1901)
Census of the Philippine Islands (1918)
Vols. I | II | III | IV.1 | IV.2 | Appendix to Vol. I
UC Press E-Books Collection, 1982-2004
This site is the only one that provides access to books that are still copyrighted. Not all books, however, are accessible, so you'll have to choose "public access books" to limit your search to the ones that are freely available. Note that books or pages cannot be downloaded, but page numbers are indicated at the end of every "page." Some of the books available are:
The United States and its Territories: 1870-1925 (USIT)
I've called this site "the best and largest online collection of Filipiniana materials available for free" before, and in some ways, it is still the best because while its name suggests a larger geographic reach, it is the only one on this list that is almost exclusively made up of Filipiniana. And while most, if not all, its titles also appear in Hathitrust, some titles can only be downloaded on USIT. One big difficulty with this site, however, is that you cannot download entire books. You can only download one page at a time. Some of the books available are:
Other sites you can check are: Biblioteca Virtual Miguel de Cervantes, Digital Public Library of America, Google Books, and Project Gutenberg.