I haven't spent much time studying Responsa Literature. Which works would serve as a good introduction? Which respona are essential to a good personal learning program?
Based on your question, it sounds like you would appreciate some halachic works that bring and reference various responsa on the topic. I can recommend the following for Masechet Berachot, which you mentioned that you were studying.
On Orach Chaim, where most of the laws in Masechet Berachot can be found there are two very valuable collections of responsa. The first is Sha'arei Teshuvah, which is printed in standard Shulchan Aruch/Mishnah Berurah books. The second is Piskei Teshuvot, which is a separate work. Both collect important responsa related to the topic at hand, and either summarize or reference various responsa. Piskei Teshuvot is more recent, and often brings very recent authorities on modern-day issues, and is extremely thorough. Sha'arei Teshuvah is much shorter, and generally brings responsa from 200-400 years ago, and many times brings those which relate to kabbalah.
There are other similar works on other areas of halacha (such as pesakim uteshuvot, pitchei teshuvah, etc.). The Bar Ilan responsa project also has a nice selection of responsa related to certain topics, although those are generally from fairly recent authorities as well. Also, many early responsa (such as those of the Rishonim) are brought by other broader halachic works, such as Beit Yosef. Hope this is helpful!
Volume I is The Responsa Literature and is essentially an introduction to responsa literature. Topics include:
- Origins and Development of the Responsa
- The Leading Respondents
- A Selection of Responsa
- Widespread Debate
- History in the Responsa
- Modern Inventions
- Curious Responsa
- Prospective Development of the Responsa Literature
Volume II is A Treasury of Responsa which consists of 63 fully translated responsa, spanning 1,000+ years of responsa writing, by 63 of the most prominent respondents in Jewish history.