Here’s a great poster of the history of life on Earth with indications of timescales and major developments. Note the indication of symbiotic events (including the formation of eukaryotes by endosymbiosis of bacteria and archaea).
HHMI also has an EarthViewer App which lets you travel back in time and see what the Earth used to be like. You need an iPad, or Android device — which I don’t have, so I haven’t been able to play with this one.
But I do have the Time Tree app, which tells you when the last common ancestor of any two types of organisms lived. You just type in “human” and “frog”, for example, to find out that our last common ancestor wats about 371 million years ago (which is about right, since that was the time of the first tetrapods).