Would stuff that's locally hosted count? You can actually download the entirety of Wikipedia and fit it into 22GB, which is well within the capabilities of an common SD card.
Maps are a bigger thing. Google has apparently collected about 20PB (20 million gigabytes) of data for maps, though I'd imagine if you just need street/address/road data that might be a significantly smaller subset. Just the satellite imagery of Google Earth is about 196TB. Not sure what just the basics would take up