Well? 
Five Live Yarddbirds (Clapton) and Roger the Engineer (Beck).
Sorry that snuck off. Marvelous guitarist though he is I thought Page was the biginning of the end for the Yardbirds - they became pretty pedestrian.
*Five Live * is what all the early buzz was about and Roger was the only worthwhile completely original album.
Live Yardbirds featuring Jimmy Page was released by Epic in the US without authorization by the group, and Jimmy Page had it pulled. It was recorded at the Anderson Theater in New York in 1968. Epic had the totally brilliant idea of overdubbing crowd ambience and applause - from what sounds like a cocktail bar. Nonetheless, you get to hear “I’m Confused”, which was the first version of “Dazed And Confused”, and you get to learn just how much Keith Relf is no Robert Plant. The record goes for megabucks, but it’s been pirated and isn’t too difficult to find on CD.
I will buy both of those, thanks.
Above advice is great, but there are plenty of “best of” compilations around. As long as you get some early stuff with Clapton, main stuff with Beck and a smattering of Beck+Page and Page, you are fine. My must-have songs include some hits, like For Your Love, Shapes of Things and Heart Full of Soul, but the rave-ups are the best, like I’m a Man, Train Kept a Rollin, I ain’t Got You, Smokestack Lightning, etc…hearing Beck tear it up on those is the best of what they have to offer.
Hey, fishbicycle old buddy - just how much is that '68 LP worth? A buddy of mine has a copy…
There is only one copy of it listed currently at gemm.com. The seller says the record is mint minus (this may be a visual inspection only and not reflect what the disc sounds like), and the cover is slightly flawed. They want $75 for it, which is a steal. I’ve seen a copy of it behind lock and key in the display cabinet at a store in Toronto, 20 years ago, for $600.
I might also suggest renting the Michelangelo Antonioni movie Blowup. Late in the movie there’s a live performance from the Yardbirds of “Stroll On” when both Jimmy Page and Jeff Beck were in the band.
My personal fave is Greatest Hits, Vol. 1: 1964-1966, which served as my intro to the band. It’s strictly early stuff, so no Roger the Engineer, but it’s a good intro to the band.
I thought I’d add that there’s a really good 2CD set on Rhino called “Ultimate Yardbirds” that you may wish to check out. It includes some singles that either weren’t on albums or are in significantly different form than their LP counterparts. It’s a lot less expensive than trying to track all of them down!