Use the .Rprofile file for such things.
for example my file .Rprofile contains :
library(geoR)
library(geoRglm)
if(!exists(".Random.seed")) set.seed(1367)
--
Ole F. Christensen
BiRC
Datalogisk Institut
Aarhus Universitet
Ny Munkegade, Bygning 540
8000 Aarhus C
Denmark