If you are buying on Steam, get HL Anthology.
Half-Life = $10
HL Anthology = $15 (HL1, TFC, Oposing Force & Blueshift - all 4 of these games are $10 each!)
I don't know about the HL1 cd... TFC came with it, but Blue Shift and Oposing Force didn't, they costed extra...
Maybe Steam does give you them for free, but I've never tried registering my HL cd so I don't know.
edit: @LegendarY, sorry I deleted my original post... I didn't really read your replies properly til after I wrote it, then I decided it didn't make sense.