והוצאתי אתכם מתחת סבלת מצרים והצלתי אתכם מעבדתם וגאלתי אתכם בזרוע נטויה ובשפטים גדלים ילקחתי אתכם לי לעם והייתי לכם לאלקים
…I will take you out from the labors of the Egyptians and deliver you from their slavery. I will redeem you with an outstretched arm and with great judgments. I will take you to be My people and I will be your G-d… 
These two verses from Sh’mot (Exodus) declare liberation 4 times:
1. I will take you out [והוצאתי] from the labors of the Egyptians
2. I will deliver you [והצלתי] from their slavery
3. I will redeem you [וגאלתי] with an outstretched arm and with great judgments
4. I will take you [ולקחתי] to be My people, and I will be your G-d.
“These four phrases of redemption are one source for the four cups of wine that we use at the Pesach Seder.” 
The four phrases aren’t simply synonymous. They’re four stages; each one greater than the one before. Commentaries (whichever we choose) and midrashim on Torah can add to our understanding of the Haggadah and Seder, too.
There’s a custom — so appropriate for Pesach — for one to pour each cup for someone else, and to allow another person to pour a cup for us. Slaves might be more likely to take what’s doled out, eating alone. How characteristic it is (or should be) of being free, to honor others by sharing with them graciously.
Last year, at a public seder I was leading, I introduced the brachah for each cup by reciting the part of the “pasuk” — the Biblical verse — that related to that cup. One could even add a comment, midrash, hasidic anecdote, etc.
Of course, prolonging the discussion of each cup of wine could be less than welcome at some seders. I leave that to your own good judgment, and the interests of your guests. Still — I urge at least a mention of why there are 4 cups and its basis in Torah.
The four cups are associated with great joy:
“Rabbi Naftali Zvi Yehudah Berlin explains that wine was chosen [as the sym- bol of redemption] because of its ability to bring a glow to the face, to brighten the spirit, and bring about a change in one’s appearance and disposition. As we drink the first cup, our hearts and faces brighten. With the second cup, the glow increases; with the third and fourth cups, our inner and outward cheer steadily grows. Similar stages of increasing joy were felt by our ancestors when they heard the four expressions of promised redemption. With each promise of liberation their faces lit up with a greater glow of happiness.” 
This is reminiscent of:
Mosheh’s face as he came down from Mt. Sinai: “…[his] face was radiant…” 
The face of the Kohen Gadol — the High Priest — as he finished his Avodah on Yom Kippur: “He was elated, his face beaming with sun-like radiance…” 
Rabbi Eliezer’s face, as he taught Torah: “[He] sat down and expounded. His face shown like the light of the sun and his effulgence beamed forth like that of Moses…” 
What common threads of light and joy run from Mosheh on Mt. Sinai, through atonement, learning Torah, and hearing the stages of our redemption?
How does it encourage hope about our own lives? About world events?