In the past, Hindu practice and belief were transmitted largely through oral tradition and localized cultural practices.
What are examples of changes in Hindu practice or belief as a result of the rise of literacy?
As the question hints at the mobilization of the Bhagavad Gita, I would like to firstly emphasize upon the same:
The expanding literacy rates have obviously helped in spreading the holy verses of the Gita en masse. Earlier, the Gita was available only in Sanskrit which was understandable only to the Brahmins as other varnas did not have eligibility to learn this. However, newer versions of the Gita contain vernacular translations of the sacred Sanskrit hymns. Thus this holy book can be read and understood by one and all, much without the help of a preacher.
The Indian Renaissance led to the eradication of Sati, the intiative being led by Raja Ram Mohan Roy and Lord William Bentinck. Courtesy goes to education once again.
However, the practice of untouchability as mentioned in earlier comments was prevalent even when education had reached Indian commoners.It was merely a taboo or stereotype which was considered quite natural. It was first brought into mainstream discussion by Mahatma Gandhi with his concept of Harijans or "The Children of the God". Education had been in the country much before Gandhiji's era.
References have also been made to animal sacrifices. It was only stopped recently with the enforcement of the Wildlife Protection Act and other legal proceedings involving concern about fauna and flora. Education was quite prominent in those years when goats, bulls and even human beings were sacrificed in the name of satisfying the Almighty.
It is not merely education that helps in changing the popular beliefs and practices. Any change requires concern and awareness, in addition to education to be brought about.
However, since the question has been specifically made about the Gita being popularized, education being spread, has indeed played a major role.
Hindu practices were always changing.. Look at the diversity of theories, counter theories, rituals, stories, mythologies, ideas, counter ideas.
The central idea to the Hinduism was always DEBATE, CONFLICT, ACCEPT, AGREE, CHANGE, and back to DEBATE again.
So, in sense your question is wrong. Literacy doesn't change religions. There are highly literate societies which have not been able to change their religion. There have been not so literate societies which have undergone remarkable change in their religious practices.
It is your sense of debate and ability to question yourself that creates change. And Hinduism has been at the forefront of that change every since the day it began. And I am sure, we will find practices in Hinduism which will starkly stand out as societies progress from where it is today. So, the central idea is to adopt , adapt and move on.
The sananthana dharma (coined as hindusim by few) is not just a practice but its the way of life for its followers. The rich tradition is spread among youngsters by the means of different festivals and functions where all the family members and well wishers take part of. Elders teach dharma through different short moral stories every day.
I can see much of the sacred texts are digitalized and brought to public. But all of these needs to be learnt through a guru who has command over the subject. I can say it has got new wings to spread the dharmic philosophy though the blogs or social networking websites. So, it is doing enough good for new generations by making them informed and connected.