I have gathered together some useful resources in one place to cover of the interesting topic of how to load balance requests to a service implemented using WCF - in response to a request from a UK ISV doing some interesting .NET 3.0/3.5 work. Frankly I wish I could have a) found a lot more or b) found one uber article that covered it in detail. But... instead the following when taken together should help.
NB: Remember, NLB (or hardware based load balancing) when combined with WCF is a simple approach that will be right for many scenarios. You need only look at creating an intermediary of some kind once you have ruled out NLB.
Firstly, you need to look at the Load Balancing WCF overview
Your own intermediary:
Alternatively the following samples represent a starting point to build an intermediary which could perform more complex load balancing
And finally, Greg Leake in the US has been working on configuration services and has recently published some of his work – this looks very relevant to this problem domain but I have had no chance to dig into it.
NB: I came across Michele for the first time while researching this - offering great advice on all things WCF. If WCF is your thing then I would recommend you look at the many great resources and posts she has created including 15 webcasts on WCF created last summer and her book on learning WCF which includes information on throttling etc. Only one left in stock at Amazon UK :-)