What lame person will skip like a ram?
Rashi: Yisrael, who are now lame and weak. We find that the weak are called Pisechim - "Pischim Bazezu Vaz" (33:23). Malbim - they will jump to Avodas Hashem and His Mitzvos.
Why will they shout?
Rashi: Due to My salvation.
Malbim: They will sing Shir Hashem.
What is "Leshon Ilem"?
Rashi: The language of Yisrael, who were mute among the Bavliyim. They hear reviling, and do not answer.
What water was cleaved in the Midbar?
Rashi: When Your salvation will rejoice them, and they will sprout like a dry Midbar thirsty for water, and springs are cleaved in it. I.e. salvation will sprout for the downtrodden.
Radak: Michah said "ki'Ymei Tzeisecha me'Eretz Egypt Er'enu Nifla'os" (7:15). This will be one of the wonders.
Malbim: There are three reasons why one cannot go in the Midbar. (a) Lack of water. (b) There is not a paved path. (c) There are evil Chayos. "U'Fduyei Hashem Yeshuvun u'Va'u Tziyon" (10), via the Midbar. These three shortcomings will depart. This refers to the first. Also refer to 35:8:7:3, 35:9:3:2.
Why does it say "u'Nchalim ba'Aravah"?
Radak: They will find much water when they return to their land.
