Technology is being used here as a noun adjunct (also called an attributive noun), which is to say, a noun being used as an adjective to describe another noun.
When nouns are used this way, they are used in the singular. Hence while a book shop will probably have more than one book, it is still a "book shop", not a "books shop".
This is even the case with nouns like scissors and trousers that are normally always plural: "Scissor sharpener", "trouser press", etc.
And hence you would want "technology websites" here.