Here is an easy one to do, the Essential Borg Invasion:
TNG 1.13 Datalore
TNG 1.26 The Neutral Zone
TNG 2.16 Q, Who?
TNG 2.21 Peak Performance
TNG 3.26-4.01 The Best of Both Worlds, Parts I&II
TNG 4.02 Family
TNG 5.23 I, Borg
TNG 6.26-7.01 Descent, Parts I&II
MOV VIII First Contact
ENT 2.23 Regeneration
Datalore and Regeneration serve as good bookends to the plotline while First Contact is a fantastic climax. This is a plot that is extremely easy to get into with only a handful of episodes and one movie. Plus its an awesome plotline, an unstoppable alien menace with a desire only for destruction invades the Alpha Quadrant and is on a course for Earth and the Federation is woefully unprepared.