Logistic pipes is already multiplayer (didn't test it, and don't know if is updated): http://www.mod-buildcraft.com/forums/topic/logistic-pipes-smp/
And thaumcraft will probably go multiplayer when the modding api in minecraft is added, and here some ideas: Redpower tunnelbore, Frames tree farm, and maybe a quarry with redpower(computercontrolled) and all the items you get are being sorted, smelted etc
And also some mods i like to see in tekkit are: Portal mod, Steve carts(will be smp soon), Logistic Pipes, ThaumCraft, MystCraft, ExtraBiomesXL, MFFS and mayhbe infitools.
Hopefully this info/tips were helpful ( and sorry if i used some bad english, its not my mother language)
Yellowthunder