For fans of old-school EV, I recommend the following.
1. Final Battle 3.0. It didn't work for me, but it might for you. Provides a vastly expanded Red Alien Menace Storyline, providing challenging missions and new outfits.
2. Eye of Orion. Again, didn't work for me (think the machine was cursed). Excellent, excellent storyline with interweaving mission strings, glorious combat, and a really cool ship.
3. The Plug With the Neutronic Kestrel. The main plot is pretty good, and the outfits are even better. Many wetting-one's-pantaloons-with-terror moments. Also includes three other plugins, such as the original Arena. Oh, and the last battle's a real @#$@#.
4. Galactic Scourge. God-like total conversion of EV. Fast-tracks the normal Rebel/Confed storylines, and adds about fifty-odd systems with six or so new races. Way too many storylines. Oh, and you get to see EARTH GET BLOWN TO BITS! COOOOOOL!
For EV:O blokes...
1. Beyond the Crescent. Great for masochists (plugin creator: "I know! I'll make Crescent Station MORE POWERFUL! Mwah hah ah hah ha!"). Brain-melting puzzles. Conspiracy-theory like plot.
2. Frozen Heart. Tachyonic Fighter make things go BOOM!
3. Femme Fatale. Great, but sort of a letdown after the Tach. sigh
4. Cloak Keep. A great little utility to have around to ensure you keep that cloak.
5. Zidagar Enhancement. Lets you buy the only worthwile outfit the Zids offer.
6. Triple Agent. Try and find a really early version to experience its challenge in full. The current version has the difficulty ramped down a million notches. Feel proud if you've managed to go through the original twice.
7. F-25. Explore, explore, explore, run away run away run away, solve puzzle, explore, explore, track down Elders so you can make the cryptic creeps pay, fight fight fight fight fight, get showered with goodies, prevent armageddon, drink milk, sleep.
8. Reign of the Voinians. Crush puny humans!