Prolog is mainly a language targeted at logical problems, especially from the AI and linguistic fields. Haskell is more of a general-purpose language.
Prolog is declarative (logical) language, what makes it easier to state logical problems in it. Haskell is a functional language and hence much better suited to computational problems.
Wikipedia on declarative programming:
In computer science, declarative
programming is a programming paradigm
that expresses the logic of a
computation without describing its
control flow. It attempts to minimize
or eliminate side effects by
describing what the program should
accomplish, rather than describing how
to go about accomplishing it. This is
in contrast from imperative
programming, which requires a detailed
description of the algorithm to be
run.
Declarative programming consider
programs as theories of a formal
logic, and computations as deductions
in that logic space. Declarative
programming has become of particular
interest recently, as it may greatly
simplify writing parallel programs.
Wikipedia on functional programming:
In computer science, functional
programming is a programming paradigm
that treats computation as the
evaluation of mathematical functions
and avoids state and mutable data. It
emphasizes the application of
functions, in contrast to the
imperative programming style, which
emphasizes changes in state.
Functional programming has its roots
in the lambda calculus, a formal
system developed in the 1930s to
investigate function definition,
function application, and recursion.
Many functional programming languages
can be viewed as embellishments to the
lambda calculus.
In short a declarative language declares a set of rules about what outputs should result from which inputs and uses those rules to deduce an output from an input, while a functional language declares a set of mathematical or logical functions which define how input is translated to output.
As for the ADDED question : none that I know of but you can either translate Haskell to Prolog, or implement Prolog in Haskell :)