How can I make my coffee taste stronger using a french press or gold filter? I like drinking my own coffee at work, as it's cheaper and more convienient than buying espresso. However, recently I've been finding myself wanting a more long-black like espresso coffee. 

How can I achieve this using either a french press/plunger or a gold filter?
I enjoy my homemade French-pressed coffee more than anything I can buy at an espresso shop, though a long black is my preferred choice if I'm away from home.

There are a couple of strengths of the espresso shop's infrastructure which you can emulate on a smaller scale:

Good coffee beans

Buy good fresh whole beans and grind them right before you prepare the drink.

Strong extraction

Use more coffee and/or grind it more finely. More surface area will make it extract more and taste stronger. You can even make it really thick and creamy and add it on top of water for the long-black-like experience.

There's a discussion about minimizing the grounds in your cup here.