Day Times

Time Associated Halachot
6:00 sAM Sunrise
Earliest shacharit
9:00 sAM Last time for shma
Last time to eat chametz erev Pesach
10:00 sAM Last time for shacharit, most opinions
Last time for biur chametz erev Pesach
12:00 sPM Last time for shacharit, if necessary
12:30 sPM Mincha Gedola
Earliest mincha, non-ideal
3:30 sPM Mincha Ketana
Earliest mincha
4:45 sPM Plag Mincha
Latest mincha & earliest maariv, according to Rabbi Yehuda
5:42 sPM Candle lighting*
6:00 sPM Sunset
Latest mincha & earliest maariv, according to chachamim

*Candle lighting time is approximate on the assumption that "18 minutes" is not an exact time but instead a general recommendation for "tosefet Shabbat", or adding a few minutes to Shabbat, so you are not lighting candles exactly at sunset. In this case, 18 seasonal minutes will be slightly more than 18 real minutes in the summer, and slightly less in the winter.

Night Times

Regrettably, and due to forces of nature quite a bit beyond our control, the times before sunrise and after sunset are tied not to seasonal hours, but to the amount of light in the sky, which is a property not of what percentage of the night has elapsed, but of how far below the horizon the sun has sunk.

As a result, it is best to think of these times in terms of "degrees" -- i.e. how many degrees below the horizon the sun is, which directly correlates to how dark it is outside. Think of 1 degree as taking about 4 minutes (true at the equator), although this can vary slightly based on latitude and time of the year. On the iPhone ZmanimClock app, you can get the seasonal and real times for most of these, customized for your location and date.

Number of Degrees Approximate Real Minutes Associated Halachot
19.75 degrees before sunrise 79 minutes before sunrise Alot Hashachar / Dawn, Israeli Minhag
16 degrees before sunrise 64 minutes before sunrise Alot Hashachar / Dawn, Majority Opinion
11.5 degrees before sunrise 45 minutes before sunrise Mishayakir
Earliest shma/tefillin
6.5 degrees after sunset 26 minutes after sunset "3 medium stars"
Earliest time to end a fast
8.5 degrees after sunset 34 minutes after sunset "3 small stars"
Shabbat Ends
16 degrees after sunset 64 minutes after sunset Shabbat Ends, Rabbeinu Tam
19 degrees after sunset 76 minutes after sunset Full darkness