Fortunately, there are now a number of fairly inexpensive ways to provide struggling readers with access to printed materials by providing text digitally, see An Educator's Guide to Making Textbooks Accessible and Usable for Students with Learning Disabilities. Once you have digital text, you have many options.
Many publishers now offer their textbooks on CD and teachers can easily scan print materials into their computer to create digital versions of texts. One of the easiest (and least expensive) ways to provide students with recorded text is use text-to-speech features built into your computer's operating system to read digitized text. These simple programs can read text files aloud for students and are freely available with all Windows and Macintosh operating systems. Although they lack more sophisticated control options and choices for speaking voices, they may be an appropriate solution for helping students read short pieces of text.
Another free option for helping students access text is to download books from a website such as Project Gutenberg or LibriVox. The books available from these sites are in the public domain, so you will not be able to find newer books here. However, they are freely available to all and may be a good solution for providing electronic versions of popular classics (Pride and Prejudice, A Christmas Carol, Alice's Adventures in Wonderland, etc.). Files are usually available in HTML, PDF or Text format, which can then be read aloud using any text-to-speech program. The Adobe Reader has a built in Read Out Loud feature which allows the user to have any part of a PDF file read aloud. You could also use this feature with any hard copy text that you scan and save as a PDF.
A third option is to obtain audio books from Learning Ally. Membership is required in order to access audio books and a special player or software is necessary to play the books. Another site, Bookshare, provides digital talking books for students of any age with disabilities. Students with qualifying print disabilities can now access the entire Bookshare collection free of charge. Additionally, audio books can be ordered from websites such as Amazon, Audible, or Barnes & Noble. However, this option will likely be more expensive than the cost of a Learning Ally membership.
The most flexible option (and also the most expensive) would be to purchase software capable of converting text files into audio files. A quick internet search will reveal several downloadable programs for running text to audio conversions. However, for a school purchase, it might make sense to investigate programs that can be used for a variety of reading and writing tasks such as Kurzweil 3000, Proloquo, TextAloud and WYNN. With these tools, you can convert any text file to a sound file; students can then listen to text using an MP3 player, their computer or CD player. Using a scanner, you can easily scan any print material and create recorded text for your students for any book, textbook, handout, or article you use in your teaching.