Yoda in the Expanded Universe

Here is Yoda's Expanded Universe biography from StarWars.com:
When Yoda was 700 years old, he served on a council of Jedi Masters instructing new students aboard the massive Jedi training vessel Chu'unthor. The starship crashed onto the planet of Dathomir. The Jedi Masters attempted to free the vessel from its swampy confines but they were repulsed by the Dathomirian Nightsisters.

Much of Yoda's history is unknown. Just prior to the dark times that accompanied the fall of the Republic, Yoda trained the Gannathan royal King Empatojayos Brand in the ways of the Force. Another student of his was the powerful and stern Qu Rahn.

During those times Yoda figured in stopping a swath of destruction cut by Dark Jedi from Bpfassh. One of these dark siders had gotten as far as Dagobah, were Yoda bested him in direct confrontation. The Bpfasshi Jedi died, his dark Force absorbing into and twisting a nearby tree -- forming a dark side nexus. It is believed that Yoda chose Dagobah as his hiding place due to the dark side energies emanating from the tree. From a distance, Force-users like the Emperor would not detect Yoda since the master's bright light side presence would be canceled by the Bpfasshi dark side presence.

Early in the Galactic Civil War, Alliance historian Major Arhul Hextrophon was researching stories about the Jedi Master when he came across evidence of Yoda's existence at the University of Charmath. Hextrophon voyaged to Dagobah, where he met Yoda. Yoda was about to erase Arhul's mind of any knowledge of the Jedi Master when he had a change of heart. Instead, he swore Arhul to secrecy, and let him depart. Aside from logging it in his personal journals, it is believed Hextrophon has not told a soul

In the Expanded Universe, Yoda's Padawans include:
a) Ikrit (approximately 400 years BBY)
b) Ki-Adi Mundi (88 - 67 years BBY)
c) Qu Rahn (around the time Obi-Wan is a padawan)
d) Empatojayos Brand (unknown exactly when, possibly between Ki-Adi Mundi and Qu Rahn)
NOTE: BBY stands for Before the Battle of Yavin. The Battle of Yavin is the first Death Star battle, taking place in Episode IV: A New Hope.

In Rogue Planet (author Greg Bear) there is a discussion between Mace Windu and this other Jedi Master called Thracia.

Here is a quote:

"It's always an honor, Thracia" Mace said

"You seem to be ganging up on this boy [Anakin]"

"It could be worse" Mace said. "Most of the Council are away today. Yoda would be much harsher-"

"That big eared tree stump knows nothing about human children. And for that matter, neither do you. You've never married, Mace! I have. I have many sons and daughters, on many worlds..."

These quotes can be found on page 47.

You can see Yoda training Ki-Adi Mundi in Dark Horse Comics' Prelude to Rebellion series. Issue #0 was avaliable to view online in Shockwave format at StarWars.com. For those of you who don't have Shockwave, or don't want to wait for it to load, here's a version that just requires an image-capable browser. When you enter, click on the pictures to get to the next part. Begin viewing the comic

Yoda also appears in the Episode I: The Phantom Menace video game for PC and Playstation.

Yoda information found in comics:
Yoda wielding a purple-bladed lightsaber
Yoda eating at Big Boy
Yoda is purple
Yoda has Luke try to chop a lightsaber but he completely misses it. Later on, he chops it in four pieces.