In Praise of Tasty Substitutions for Salt
 

I love finding ways to season my food without using the salt shaker. I often use anchovies as a seasoning. Generally, folks can not even taste the rinsed anchovies. Another good substitute is Feta cheese. Tonight I roasted broccoli and crimini mushrooms in olive oil, garlic and dried chilis. At the time of serving I added crumbled Feta to the vegetables. That was all the salt the dish needed.
Parmesan is another great salt substitute. I use the rind of the parmesan cheese to flavor Minestrone. No added salt is required.

But all your examples are high in sodium -- so it is just salt in another form. For sodium-free substitution, try lemon juice, lemon pepper, lemon thyme or even balsamic vinegar. Commendable thread, but "no added salt" isn't really the objective, rather reducing the total sodium content.

You raise a really good point. It was not my intent to look for low-salt substitutions. I just like food which tastes great and adds a bit of a salty flavor. More interesting than shaking the Morton's box over the roasted veggies.

sriracha hot sauce adds a nice kick to almost anything.

I sometimes stir in a little anchovy paste into a sauce. No-one is the wiser;) Adds a bit of punch to a sauce. Capers also work.

This was going to be my suggestion. Works great, especially on vegetables.

anchovies, cured hams, fish sauce, soy sauce, mustard are all good options, depending on what sort of flavor profile you are trying to achieve.

Also, if trying to reduce salt, adding acid to a dish at the end can help brighten it up.

I was going to say soy sauce too, but that's actually salt, isn't it? :)

We're not looking for substitutions for salt (even though the OP titled the thread "substitutions for salt") but apparently for things that have salt along with other flavors.

kalamata olives are great too.

A couple weeks ago, I baked some boneless skinless chicken breast with slices of lemon and kalamata olives.

As mentioned, most of the substitutes described are simply salt-laden, either in their formulation/packing or naturally in the case of cheeses.

I find the "fish sauces" (Nam Pla, etc.) to be addictive and interesting in a variety of dishes, not just seafood, although many are put off by the fishy aroma and taste. But, like anchovies, they get their salty punch from plain old salt (and, let's face it, almost all salt is "sea salt", the only difference being the time away from the sea).

marmite
soy sauce
fish sauce
worcestershire sauce
dashi concentrate
miso
olives and capers for that puttanesca vibe
parmesan
tomato sauce

All wonderful!

However, when avoiding salt completely, these options also work for me:
garlic
smoked paprika
ground toasted sesame seeds (or sesame oil)
making dashi from scratch using kombu and katsuobushi (there is salt in katsuobushi but it's minimal - something like 0.4%)
dried cep/porcini or dried shiitake

This list is mostly about umami flavours. Anything with a strong umami taste is going make things taste good.