Chrome itself has some features that can be turned on, such as spoken feedback, high contrast mode, and screen magnification. Learn how to (easily) turn that on in Chrome help.
Voice Search is now available on all platforms (iOS, Android, browser) - simply click the microphone icon in the search bar and speak the search terms desired. I use this quite a bit on my Nexus phone and it works surprisingly well.
Black and White is a Chrome theme that can be installed which limits the colors on the page to black, white, and some blue.
Chrome Reader app (Android) will read Chrome browser pages on Android smartphones. Here's a YouTube review.
AppWriterCloud ($20 per year, one month free trial). Features include context-based word suggestions, phonetic spelling, text to speech with color highlights and a webreader that will also read ocr-processed pdf files opened via Google Drive.With a 1 month free trial, would certainly be worth checking out.
Here's an extensive list of apps from GDRSD Edtech Commons for Chrome (and a separate one for iPad) well worth reviewing.
I found one interesting app there called OpenDyslexic, which will override all fonts on a Chrome page to be easier to read for people with dyslexia.
Here's one more list from the Everyday Speech blog you'll want to look at - more good ideas for people needing some reading comprehension support, those with hearing issues, and much more.
Please note that I have NOT had the chance to test most of these myself. I would love some feedback about these, and accessibility tools and other options you've found.