The holiday is charcacterized in Torah shebikhtav two ways: Shavu'ot, since it occurs seven weeks after Pesah, and Yom Ha-bikkurim, the day when the first of the wheat crop was brought up to the Beit Ha-mikdash and given to the Kohanim. The Mattan Torah angle apparently is post-exilic, a cultural accretion that developed when we no longer had a Beit Mikdash and therefore could not bring Bikkurim.
Shavu'ot is also referred to in the Mishna is Atzeret, a conclusion. Just as Sh'mini Atzeret is the conclusion of Sukkot, Shavu'ot is a conclusion of Pesah. We've all heard, and most of us will hear again tomorrow or the day after, drashot explaining that the purpose of yetzi'at Mitzraim was fulfilled with Mattan Torah seven weeks later. Freedom without law is not freedom but chaos. Without detracting from this explanation, I would like to offer an additional one. As slaves our lives were not our own; we did what our masters told us to do when they told us to do it. Even our food was dictated by our masters, who set a pot of food in front of us the way one would feed animals (see the commentaries on sir ha-basar, the fleshpots of Egypt). The fruits of our labor belonged not to us but to our oppressors. As free men, our lives would be very different. We would have our own country, work its soil, and enjoy its produce. The temptation to attribute our success to our own efforts - kohi v'otzem yadi (see Parshat Eikev) must have been strong. Therefore, we were commanded to take the first fruits of each year's crop, bring it up to the Beit Ha-mikdash, and recite a confession which became the basis of the Haggadah Shel Pesah [see the beginning of Parshat Ki-Tavo]. But the Haggadah stops in the middle, after the miraculous deliverance from Egypt. The remaining verses are not read at the Seder: And He brought us to this place, and He gave us this land flowing with milk and honey. And now I brought the first fruits of the land that You, Hashem, gave me, and he [the one who brings the Bikkurim] shall leave it before Hashem your God and He shall bow down to Hashem your God. And he shall rejoice in all the good that Hashem your God gave you and your house. . . . Shavu'ot becomes the conclusion of Pesah, in that we confim our freedom by thanking Hashem for the privilege of working our soil and eating its produce, and acknowledge that our material success comes from Hashem! Is this the same people that developed a culture of parasitism where working for a living is denigrated and the ideal is to study Torah full time and live off the labor of others? If I had my druthers we would be reading Parshat Ha-bikkurim on Shavu'ot along with the Ten Commandments.
The Bikkurim were to be brought up in a basket, in Hebrew not the usual sal (as in kadursal, basketball), but a tene, a word that sounds Egyptian. A tene held things. It resembles a Latin root meaning "to hold," i.e. tenir in French. In English the word "tennis" originates from the racket that a tennis player holds in his hand, and Cold War defeatists told us that West Berlin was untenable, we couldn't hold onto it. I wonder if the Hebrew-Egyptian and Latin words are related, or if they simply resemble each other by accident. At any rate, in a good year the contents of a tene must have been heavy, and it had to be held in the hand at least the final few hundred meters to the Beit Ha-mikdash. Shavu'ot - Yom Ha-bikkurim was no holiday for Jewish weaklings!
Let us pray that we will soon celebrate Shavu'ot as we were commanded, as normal Jews in a normal country once did, with heavy baskets carried on strong Jewish shoulders to the rebuilt Beit Ha-mikdash, quickly and in our time.