ggplot contains an incredibly rich and powerful set of tools for visualizing data. But ggplot and base R are not your only options! A variety of packages exist for visualization, including:
Several packages have been created that build off of ggplot’s syntax with additional functions. You can find a list of them here.
Several analytical packages come with their own plotting functions that produce some very nice visualizations. There are dozens out there, but a few of them are visreg for regression plots, corrplot (and its ggplot counterpart, ggcorrplot) for graphical presentation of correlation matrices, and rpart.plot as a companion to the decision tree package rpart.
Increasingly, scientific journals are providing platforms for interactive graphics on their websites to accompany published articles. Interactive plots are also popular for personal, lab, and organizational websites, and they can provide another option for your own data exploration. Two of the most popular in R are plotly, which offers a huge variety of 2D and 3D plots, and leaflet, which is specifically for mapping.