Vanguard also offers a solo 401k. You can contribute $18k per year to it ($18k total among all 401k's you have), but you can also contribute 20% of your self employment income (after subtracting your self employment tax--so around 18% total) on top of that, up to $53k per year. So if your independent contractor job pays you $40k, you can contribute around $18k+$7k to it for the year, in addition to your IRA.
I have thought about self-employed/solo 401k options but aren't these worthless if I take on a salary position with a company (employee)?
Depends on how you define "worthless".
From
http://www.irs.gov/Retirement-Plans/One-Participant-401%28k%29-Plans:
Contribution limits in a one-participant 401(k) planThe business owner wears two hats in a 401(k) plan: employee and employer. Contributions can be made to the plan in both capacities. The owner can contribute both:
Elective deferrals up to 100% of compensation (“earned income” in the case of a self-employed individual) up to the annual contribution limit:
$17,500 in 2014 and $18,000 in 2015, or $23,000 in 2014 and $24,000 in 2015 if age 50 or over; plus
Employer nonelective contributions up to:
25% of compensation as defined by the plan, or
for self-employed individuals, see discussion below
If you’ve exceeded the limit for
elective deferrals in your 401(k) plan, find out how to correct this mistake.
Total contributions to a participant’s account, not counting catch-up contributions for those age 50 and over, cannot exceed $52,000 for 2014 and $53,000 for 2015.
...
A business owner who is also employed by a second company and participating in its 401(k) plan should bear in mind that his limits on
elective deferrals are by person, not by plan. He must consider the limit for all
elective deferrals he makes during a year.