Fidelity for one, has self-employed 401(k), regular employee 401(k) and various versions of IRAs.Quote from Toonces:there are very few brokers that allow you to trade a 401-K, whereas it seems that just about any broker will alow you to trade an IRA.
In their self-employed 401(k) and various IRAs you can buy stocks, options, and so on. I've not noticed any discernable difference between them at Fidelity.
Most of the noticable restrictions are due to the free-riding rule because you have a cash account, rather than a margin account.
So it depends maybe on what type of 401(k) you mean, what broker you want to use, what investments you want to be buying, and how long you wish to hold them and how long you will wait until redeploying the sales proceeds.