Can I do anything?

Let us assume for the first part of this answer that your husband's father did in fact put his daughter's name on all his assets (i.e. it was not forged or fraud that her name was on them) and that he was mentally competent when he did so. In that case, there is nothing to do. A will has no power until the person making it (the "testator") dies. Prior to his death, the person can spend, use up, give up or gift, sell, etc. his assets however he wants, and the will does not prevent that. A will should be read as saying in essence, "Anything I still own solely in my own name and is not pay/transfer on death [i.e. POD or TOD] will be inherited as follows....." In this example, your father-in-law ("FIT") had the right to make his daughter the joint owner of his house, his car, his bank accounts, etc. even if doing so was unfair or unwise. Having made her the joint owner, when he passed away, those things did not become part of his estate, where not divided according to his will, but rather immediately and automatically became hers.
Alternately, if you feel that she threatened or coerced him into putting her name on the assets, or she tricked him (fraud) into doing so, or forged his signature to do these things, or that he was not mentally competent when this was done, your husband could try to challenge those actions, invalidate them, and therefore get his share. But bear in mind:
1) First, after two years, it may be too late to bring this sort of challenge, depending on the exact timeline and facts. Even if not too late, your husband will be running out of time and would have to act soon.
2) You'd need evidence to prove or support your challenge (such as of threats, force, mental incompetency, or forgery); even if you are 100% certain that the actions should be void, unless you can prove your case, you can't invalidate them.
3) The only way to invalidate those things would be by a lawsuit (where, as above, you'd have to prove your case). Assuming the sister fights (doesn't give up), the case could be long, expensive, acrimonious, and winning is not guaranteed. 
Trying to get "his share" is not a decision made lightly. If you and your husband have reason to think his father was mentally incompetent or the sister did something illegal, consult with an attorney about the situation to see if 1) you still have time for a challenge, 2) what evidence you'd need, 3) the odds of winning, and 4) how expensive the case would be to bring. Then you can decide what to do.