What are the best Room Accustic Treaments members have found?

I  am looking into adding some room acoustic treatments to my room.  I am just looking for advice on some simple room treatments that fellow members found worthy of purchase. 
I will add to the list of supporters for GIK products. I have found the products attractive with a good selection of fabric colors, fairly priced, great customer support and quick delivery. Some of the pieces are large and appear that they would be heavy, but in reality are very light for their size.
I suggest going with bass traps in the front corners and two side panels for mounting on both side walls slightly in front of each speaker (first reflection point) as a first starting point.
If you sit very close to the rear wall then you probably should add another wall panel right behind your head centered on that wall assuming you are sitting centered to the wall.
The wall panels in my opinion should be the thicker ones to cover a fuller frequency range. The thin ones are mainly for the higher frequencies.
This should get you started with a quality product.
I have one of the newer Stillpoints Apertures placed on the floor between and slightly behind my speakers.  Helps to focus the image and enhances coherency of the whole presentation. I enthusiastically recommend giving it a listen. Domestically, I appreciate being able to easily slide it away next to my equipment rack when not listening.
I have both GIK bass panels and corner traps and ASC Tube Traps. The ASC Tube Traps, though more expensive, are by far and away the more effective of the two. So much so that the GIK corner traps and some of their bass absorber/diffuser panels are now out of the stereo room and are in the family room with the AV system.
The workmanship is also much higher with the ASC products. I was disappointed in the overall workmanship of the GIK products, which came from the factory with exposed staples on some panels, wrinkled seams, and front decorative diffuser panels improperly fastened and bowed.

Eight 3' Tube Traps (two stacked in each front corner, with their diffuser side turned toward the sweet spot; two stacked to the outside of each speaker in the plane of the speaker fronts) made more improvement in the overall sound from top to bottom of my stereo than any component-level upgrade I've done.

Though not cheap, ASC products sometimes go on discount for show samples and clearance.
Good luck,
Steve Z
My suggestion would be to find out what your room is doing before seeking solutions to issues you may or may not have.  If you live near a local B&M store that installs home theatres, or an AV installer, chances are they have a program that will analyze your room. They should do this for a reasonable price - you are basically asking them for a quote to treat your room with whatever is needed and they will make suggestions about what sonic measures should be taken.

Whether you accept their bid to do the job or not, you have to be prepared to pay a reasonable fee for their time and expertise to analyze your issues.

If you still want to do it yourself, come back here and ask specific questions about what you need to do to rectify specific issues.
Wall placement as required by speaker setup reccomendation, reasonable amount of furniture and wave breakups, such as bookcases filled with books, and damping material placed strategically on walls, ceiling if hot spots (excessive refections) found.  Do this, and you will have a decent setup.  After that, it is all refinement and experimentation.