Lucy just isn't the lone fossil anymore. There are now over 4,000 hominid fossils that have been found (Lubenow 1992). Of those, about 150 are Homo Erectus, 90 Australopithecus robustus, 150 Australopithecus afarensis, and 500 Neanderthals. That is as of 1999, if anyone has a more updated count please let me know. Then, just recently in 2009, Ardi Ardipithecus ramidus was found, a hominid species from 4.4 milllion years ago.
I was originally going to lay out all the evidence in this post but I figured people like visual evidence, not something that's explained out to them. It needs to be real in their eyes. Also, the videos at the bottom in my opinion did such a wonderful job at showing the transitions of hominid species. Make no mistake about it. Human evolution is alive.
Here is a figure showing many of the hominid skull fossils that have been found. There has been many many more fossils found recently along with complete skeletons that are not shown in the diagram. The first skull is that of a chimpanzee (A), our closest living relative, for comparison. Notice how as time goes on, the frontal lobe starts to increase in size, giving rise to a larger pre-frontal cortex which is responsible for planning, decision making, and higher order thoughts.
(A) Pan troglodytes, chimpanzee, modern
(B) Australopithecus africanus, 2.6 Million Years
(C) Australopithecus africanus, 2.5 Million Years
(D) Homo habilis, 1.9 Million Years
(E) Homo habilis, 1.8 Million Years
(F) Homo rudolfensis, 1.8 Million Years
(G) Homo erectus, 1.75 Million Years
(H) Homo ergaster, 1.75 Million Years
(I) Homo heidelbergensis, 300,000 - 125,000 Years
(J) Homo neanderthalensis, 70,000 Years
(K) Homo neanderthalensis, 60,000 Years
(L) Homo neanderthalensis, 45,000 Years
(M) Homo sapiens, Cro-Magnon I, 30,000 Years
(N) Homo sapiens, modern
This diagram illustrates which species lived during the same. Whether or not any of these species ever came into contact with each other is still highly debatable and unknown. However there is some minor evidence suggesting that homo sapiens may have made contact with neanderthals. The neanderthals died out about 30,000 years ago from unknown causes.
Here are two very good videos (with lousy music) walking you through each of the many known hominid fossils and showing the transitions. Please watch and enjoy your family history: