Java fern--you can glue it to any of your decorations (dry them completely, use straight superglue with only cyanoacrylate).
Anubius--same as the java fern, or you can put them in the substrate, just make sure the rhizome--the bit that the roots and leaves come out of--is above the substrate level and only the roots buried.
Crypts
Bacopa monnieri (Moneywort)
Bacopa carolina
Anacharis/elodea
Hornwort and Pennywort--floating plants
Aponogeton--most big box stores have them in bulb form. Push them into the substrate and let them go. I usually have about an 80% sprout rate, but once they sprout, they start making bulbs of their own.
Wisteria
Water primrose--I've had so so luck with it, but others have probably have had better luck.
Hygrophila compacta
Java moss
Bamboo plants
That's all that's in my tanks that's not a sword of some sort, and I only do low light with some fertilizing. Anubius is personally my favorite--there are multiple types, so you can get an interesting mix just in that group alone, and for me so far they've been bombproof. Slow growers, but steady. I have a few ludwigia species in one tank, but I'm not certain I have enough light for them to feel completely comfortable recommending them in a low light low tech tank. Give me about 6 months and I'll get back to you on it.