Before we begin the Shemoneh Esreh each morning, we say the blessing, "Blessed are You, Hashem, Who redeemed Israel (Ga'al Yisrael)." Then within the Shemoneh Esrei itself, in the "Re'eh va'ahneynu" section, we conclude "Blessed are You Hashem, Redeemer of Israel (Go'el Yisrael)." Aside from the use of the past tense and the present tense, there doesn't seem to be much difference in the blessing. Moreover, as I understand it, our tradition is to not to say anything between the blessing of Ga'al Yisrael and the Shemoneh Esrei so that we don't make a break in the connected concepts of redemption and prayer. O.C. 66:7. What is the substantive difference between these two blessings, if any?
The first, recited before Sh'mona Esrei, is a b'racha of praise and testimony. We are blessing Hashem for having redeemed us from Egypt. Ga-al Yisrael is in the past tense and means "who redeemed Israel".
The b'racha in Sh'mona Esrei is a request to be redeemed now. Go-el Yisrael means either "Who redeems Israel" or "Redeemer of Israel".
One major difference, according to some commentaries (Rashi to Megillah 17b, Ein Yaakov), is that the beracha of גאל ישראל is referring to national redemption, whereas the beracha of גואל ישראל is referring to individual redemption from personal suffering.