Dr. Squat - Dr. Fred Hatfield

Sissy squats

Hip belt squats (buy an ironmind belt)

The squat has a number of variants, some of which can be combined (e.g. a dumbbell split squat):

Back squat - the bar is held on the back of the body at the base of the neck or lower across the upper back. In powerlifting, the barbell is often held in a lower position in order to create a lever advantage, while, in weightlifting, the barbell is often held in a higher position in order to keep the torso more upright in a deep squat. These variations are called low bar and high bar, respectively.
Front squat - the weight (usually a barbell) is held in front of the body across the clavicles and deltoids in either a clean grip, as is used in weightlifting, or with the arms crossed and hands placed on top of the barbell.
Overhead squat - a barbell is held overhead in a wide-arm snatch grip; however, it is also possible to use a closer grip if flexibility allows.
Box squat - lifter sits back onto a short box, momentarily relaxing the hip flexors, before contracting them and rising off the box;[8] the use of a box sets a consistent depth and increases emphasis on the muscles of the posterior chain.
Zercher squatt - the bar his held in the crooks of the arms, on the inside of the elbow.
Hack squat - a barbell is held in the hands just behind the legs; it was invented by early 1900s professional wrestler Georg Hackenschmidt.
Sissy squat - a dumbbell is held behind the legs while the heels are lifted off the ground and the torso remains flat while the lifter leans backwards; sometimes done with a plate held on the chest and one arm holding onto a chair or beam for support.
Pistol squat - a freestanding one-legged squat where the non-lifting leg is held in free space.
Split squat - an assisted one-legged squat where the non-lifting leg is rested on the ground a few 'steps' behind the lifter, as if it were a static lunge.
Bulgarian squat is performed much like a split squat, but the foot of the non-lifting leg is rested on a knee-high platform behind the lifter.
Hindu squat - is done without weight where the heels are raised and body weight is placed on the toes; the knees track far past the toes.
Jump squat - a plyometrics exercise where the squatter jumps off the floor at the top of the lift.
Air squat - done with no weight or barbell, often at higher repetitions than other variants.

i absolutely cannot do deadlifts anymore.

i will try some of these but looks like most of the excercies Dr Squat suggested put pressure on the spine in one way or another.

Pistol squats, now that's a challenge!

Step ups using dumbbells are great, both the peterson version Todd mentioned and onto a higher step to work the backside more.

How about sled pulls using a hip harness, those are both challenging and fun. You can do them forwards, backwards, and laterally. For a real hamstring burn, try them moving forwards standing straight up.

In addition to your standard forward lunge using dumbbells, try walking lunges, reverse lunges (big step back), and lateral lunges.

You can also do some abductor/adductor movement lying on your side with a dumbbell or standing with band or cable resistance.

Lastly, a good quad exercise is a wall squat using a stability ball or medicine ball (to roll up and down the wall with) and using dumbbell resistance.

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