Beginner/easy plants

Water sprite, water wisteria, java fern, java moss, hygrophila, hornwort are all hardy and not demanding.

I list these as they are good beginner plants that I still use them frequently.

I don't have much light in my 20 gallon tank and I'm using regular old white sand with no dosing. The plants that are growing really well for me are water wisteria, rotala rotundifolia, hornwort, anubias nana, java moss, and crypocoryne undulata or wendtii.
The plants I have that I'm struggling with are ludwigia repens, stargrass, cabomba, Blyxa japonica, mayaca.
I highly recommend anubias. Beautiful and bulletproof.

Jungle val works nicely too. Just one plant will reproduce into many through sideshoots. I have some in my 2 gallon nano that has a very small bioload with no ferts dosed, and it has reproduced in those conditions.

Sagittaria, water sprite, wisteria, anubais, java fern, jungle val, some crypts, ludwigia (In my experience)

Ludwigia repens x acruata grows like a weed for me and my friends in every single tank we put it in. We started with 1 stem as a freebie and now have tons. I pull out handfuls of 1ft trimmings from my 20l every other week.

It also looks pretty nice, gets a nice red/bronze color to it.

I agree with the majority. Easy plants, in my experience, have been: Water Sprite, Java Fern, Java Moss, Anubias (specifically Congensis), Ludwigia Repens. Good luck & have fun!

Myriophyllum aquaticum, known as "parrots feather", is very easy. It's a long stem plant that is similar to Cabomba with soft, feathery leaves. It can be an effective center piece if planted in a tight bunch. It's a noxious week that can be found in lakes and waterways throughout the US. I got mine from some lakes in the local park. Here's a map if you live in one of these states:
http://plants.usda.gov/core/profile?symbol=myaq2#

Wanted to update the question. What are easy stem plants to keep? I already have wisteria and I'd like to avoid anacharis.

http://www.plantedtank.net/forums/showthread.php?p=498666

v3

I am going to agree with the majority.

Anubias, java moss, cryptocoyrne Undulata, water sprite, water wisteria are all in my low light tanks and going good.
I overtrimmed my water wisteria when I first got it, but its made a good comeback. LOOOONNNNG root systems when I pulled it up to trim and replant today.

And my water sprite is going strong too, only about 2 months ago I trimmed some baby plants off of it and replanted, and today I had to heavily trim all of the babies to keep them under control.