The parsha Ki-Seitzei contains an assortment of mitzvahs in many different areas of life.
In the first aliyah, the Torah gives the procedure to follow if a Jewish soldier is attracted to marry one of his captives of war. The law is designed to account for the Evil Inclination, but yet discourage such a marriage.
The aliyah then goes on to discuss a law of inheritance, and the law of the rebellious son.
The second aliyah discusses aiding our neighbor when we see his animals running away or under a burden.
The aliyah ends with the mitzvah of sending away the mother bird when we take its chicks or eggs, and the reward is specified as a long life. Since the mitzvah of honoring one's parents has the same reward of a long life, it's been said that this mitzvah, the chasing away of the mother bird, the easiest mitzvah, and honoring one's parents, what some consider the hardest mitzvah, both have the same reward. Therefore we can conclude that it this also the reward for every mitzvah in between.
The third aliyah begins with the words "when you build a new house", and the previous aliyah ended with the mitzvah of sending away the mother bird. Rashi says that the fact that these verses are adjoined in the Torah means an additional reward for sending away the mother bird, and that is that you will build a new house. This aliyah goes on to specify the mitzvah of building a fence around a flat roof so that no one will fall off.
The aliyah then goes on to discuss some prohibited combinations. It mentions the prohibition of mixing seeds in planting, or of different species of animals plowing together. Here also is the prohibition of shatnez, which is wearing a garment containing both wool and linen, which is why we bring certain new garments to a "shatnez" checker before wearing it.
Finally the aliyah discusses some prohibited relationships between people and the prohibition of a mamzer (which is a child born from an adulterous relationship) from marrying a Jew. This underscores the urgency of a couple who is divorced only in a civil manner, to also get a kosher Jewish divorce (a "get") because without one, a subsequent relationship could be considered an adulterous relationship, causing any offspring to be mamzerim.
The fourth aliyah discusses some aspects of cleanliness of the Jewish camp, because, as the Torah says here, G-d walks in the Jewish camp.
Included here is the Torah prohibition of female prostitution and male sodomy. It also prohibits here the loaning for interest to a Jew, but interest may be charged to a non-Jew.
Finally, this aliyah says that everything that comes out of one's mouth is like a vow, and must be carried out. Therefore, we must always be careful to say "blee neder" (without a vow), or "Im Yirtze Hashem" (G-d willing) whenever we say we're going to do something. This is so that if it turns out we are prevented from doing that thing that we said we would do, we won't be breaking a vow. In a similar vein, Judaism says that we can never underestimate the power of a blessing, or (G-d forbid) of a curse, of even a simple Jew. The power of our blessings should not be taken lightly, and we are forbidden from ever uttering a curse.
The fifth aliyah gives the Torah sources for the laws of divorce. A Jewish divorce requires a written get, placed into the woman's hand. Furthermore the divorced couple can't remarry if the woman remarried in between. The divorce of a Kohen is more complicated, he can't marry any divorced woman, even his own ex-wife. Therefore the "get" process of a Kohen is more involved to prevent "anger of the moment divorces". An interesting fact is that the Gomorra derives all of the Halachas (laws) of Jewish weddings from these few verses in the Torah about divorces.
The sixth aliyah begins with a very nice mitzvah (as all mitzvahs are), of when a man marries a new wife he is exempt from any kind of service in the army, and he is to make his wife rejoice for a year. Yeshiva students go to kollel for a year after marriage and they don't go to evening classes that first year. Here also one finds one of the six remembrances (remembering what happened to Miriam) that are found on page 86 of the siddur Tehillat Hashem, and some laws of lending.
The seventh aliyah contains the mitzvah of Yiboom, where, if a married man passes away and has no children, his brother is obligated to marry his widow. If the living brother refuses to marry the widow, he and she go through a Chalitzah ceremony where, in front of the elders of the city she approaches her brother-in-law, takes off his shoe, and spits towards his face. Nowadays, in this situation, a brother-in-law no longer marries the widow, but they still go through the Chalitzah ceremony using a specially made shoe that is kept just for this purpose, even today. So if you know anyone who might, G-d forbid, be in this situation, they should contact an Orthodox rabbi and find out what to do.
In the maftir aliyah is also one of the six remembrances that conclude the morning prayer on page 86 of the siddur Tehillat Hashem. This mitzvah is to remember what Amalak did to us on our way from Egypt, and that we must eventually obliterate the memory of Amalak. Chassidus teaches that we all have a little bit of Amalak within each of us as the source of our evil inclination. Since the word Amalak has the gematria of 240, and the word for "doubt" (safek) also totals 240, we can see that whenever we have a doubt about doing a certain mitzvah, or even if the doubt just dampens our enthusiasm for a mitzvah, that's our internal Amalak doing that to us. And here the Torah is enjoining us to obliterate the Amalak within us.