Well, if you want Intel then go for a P4 2.4GHz indeed, the best choice right now and if you can get one made in CostaRica, they OC very well to 3GHz.
As for the board, I would suggest the EPoX 4PEA+ and some PC3200 RAM to go along with it, that is if you want overclocking. If not, standard PC2700 RAM should do. Good brands for RAM are Samsung, Crucial, Mushkin, Corsair, TwinMOS(not necessarily in that order).
If you want to go with AMD Athlon XP, then one of those new 2400+ CPUs will be a good choice, or the older 2000+ if you want cheaper.
For motherboard, either ABIT's KX7-333 or the newer KD7, or better yet EPoX's 8K9A2+(KT400 with LAN, Serial ATA, RAID etc) or the older 8K5A2+(KT333 with RAID, USB 2.0, LAN, sound etc) or the older yet very good 8K3A+(KT333). Same RAM applies here....
And note that I for one have had very good experience with EPoX boards and ABIT boards, but lately ABIT boards dissapointed me a lot.