1. Give a copy of Quran to someone and each time they read from it, you will gain hasanaat.
2. Donate a wheel chair to a hospital and each time a sick person uses it, you will gain hasanaat.
3. Share constructive reading material with someone.
4. Help in educating a child.
5. Teach someone to recite a dua. With each recitation, you will gain hasanaat.
6. Share a dua or Quran CD.
7. Participate in the building of a mosque.
8. Place a water cooler in a public place.
9. Plant a tree.Each time any person or an animal sits under its shade or eats from the tree, you will gain hasanaat.
10. Share this with someone. If one person applies any of the above you will receive hasanaat exponentially, InshaAllah.
...Just to add to the list, I think that one of the best things a person can do is teach another Muslim how to make wudu and/or salah. This is because you can pretty much guarantee a constant influx of good deeds being written down for you at least 5xs a day, InshaAllah. Then imagine when this person gets married and has children, and they teach their children how to make wudu and pray, InshaAllah.... SubhanAllah, think about the ajr(reward). InshaAllah that would be a source of hasanat until Youm ul Kiyama... MashaAllah. So lets purify our intentions and share our knowledge and the beauty of this deen with as many people as we possibly can... and don't forget to smile while you're doing it because smiling is charity and sunnah at that!
Abu Huraira (ra_ reported that the Rasul(saw) said: "When a human being dies, all of his deeds are terminated except for three types: an ongoing sadaqah, a knowledge (of Islaam) from which others benefit, and a righteous child who makes du'aa for him." (Muslim and others).
Abu Qataadah(ra) reported that the Rasul(saw) said: "The best that a man can leave behind after his death are three things: a righteous child who makes du'aa for him, an ongoing sadaqah whose rewards continue to reach him, and a knowledge that continues to be implemented after him." (Ibn Maajah, and others. Verified to be sahih by al-Mundhiri and al-Albaanee)
Keep those scales heavy with good deeds inchallah!! ^_^