If I have fresh limes on hand but not fresh lemons, can I use the limes to make hollandaise and mayonnaise? Assuming it works, what effect will the lime juice have on flavor and texture?
Yes, it will work. The texture won't be different but the flavor will be significantly different. It will taste like lime hollandaise. :-P
I imagine a lime hollandaise would taste great on fish and other seafood. I'm not entirely sure what you would do with lime mayonnaise though.
Yes of course you can. As hobodave says above, lime hollandaise would be lovely with seafood, specifically crustaceans, scallops, and skate. Lime mayonnaise would, I think, be lovely in any dish using Mexican or Tex-Mex flavour profiles.