What are good successive assignments for squad leaders, besides other leadership positions?

Company Operations Sergeant
Supervisory Training NCO
Broadening Assignments such as Drill Sergeant, Recruiter, Small Group Instructor
Any staff positions (relevant to MOS and unit requirements) at BN or BDE-level

Good question, sir. A lot of raters and S/Rs are struggling with this section of the 2166-9

1SG Healy, thank you, those are good and I will use one or two this rating period!
Chief Baker, specifically for Engineers.

I have a SL that who I am not comfortable with being a platoon sergeant. He is a great 12R (electrician) and he does this Civillian side (This is from the National Guard perspective) but his leadership skills are greatly lacking. Commonly my PSG has to bypass him and get information from his E-5's as well as rely on them to delegate. If this sounds odd, I assure you it is not uncommon in the reserve components at least from my experience (which, seeing as I am a Lieutenant citing my 'experience' can be taken with as much salt as you desire). But none the less its extremely frustrating.

I have seen HAZMAT and EO NCO's get lucrative offers to work in Corporate America.

Have the Soldier show you their Army Career Tracker (ACT) with jobs specific to their MOS. This is a good place to start. A conversation with the Soldier helps. Once you have your plan take it to the PSG or 1SG or CSM for a sanity check.

You have an ACT career map as well

Instructors (NCOES or MOS), IG's office (though I'm not sure what the minimum rank is).

Head to TRADOC. Recruiter, Drill Sergeant, and the best experience generator of all .. Observer / Controller at NTC (heavy / light) or JRTC (light).

That really depends on the MOS and branch sir! I mean in aviation they may go to maintenance or shops to broaden their knowledge as an inspector. At times others have been assigned outside of the MOS per the mission requirements. It really is MOS dependent and which branch are you really interested in?

Army Master Fitness Trainer

what are good successive assignments for IT

Depends on the MOS, Each MOS manual has the career path near the front of the book. It shows what schools, assignments, special duties and civilian education support career progress and when in a Soldiers career they should look to hit those items and milestones.