Getting back to the topic...
I've recently been playing on "Grid" maps and deliberately picking home systems that have at least 10 wormholes just to enjoy this kind of situation. My list:
1. Teleport Battle Stations are your personal saviour, of course. But they're just one bonus ship and not always available.
2. When wormholes are common, you can often position turrets so they cover multiple entrances. It's worth doing this just to guarantee you'll get some potshots at incoming ships no matter what. In particular, missile turrets have good range and shoot down bombers, which is essential because...
3. Fortresses are the best and most reliable answer that is always available. Huge range, mobile, lots of HP, gives mobile repair. With a fortress around, you mostly only need to worry about bombers, which are practically immune to fortresses, and vampire claws, which are 100% immune to fortresses (missile immunity).
4. Mines. Yes, mines. Two reasons: First, they cost no energy. Second, it only makes sense to put mines around wormholes anyway, so a system with lots of wormholes gives you an easy place to put them. 50 mines per wormhole is a good rule of thumb, and the default single-player cap of 1020 mines is perfect for a 20-wormhole system. Area mines are especially good at wiping out warp raids, and will instantly wipe out almost all Mk I raids while severely weakening anything tougher. I actually have a game where area mines were my MVP in total kills because I had two systems with 12+ wormholes each that were both extensively mined and repeatedly subject to warp raids. When you're more worried about Special Forces, EMP mines might be better, since they delay enemies while you clean house and rebuild.