Big Download is running an article on fifteen indie game recommendations that you should own at least half of for the holidays, with a couple of them a bargain at $20 or less per title (all prices are in USD):

Audiosurf - $10
Aquaria - $30
Noitu Love 2 - $20
Samorost 2 - $6.60
Cortex Command - $18 ( * $9 only for a limited time)
Harvest: Massive Encounter - $25
Armageddon Empires - $30
Mount and Blade - $30
Deadly Rooms of Death: Journey to Rooted Hold - $20
Everyday Shooter - $10
Spirit Engine 2 - $18
Immortal Defense - $15
World of Goo - $20
Multiwinia - $16.60
Lugaru - $20

* Dan had actually reduced the price of Cortex Command from $18 to $9 starting today, although the offer is only valid until the end of this weekend.

Feature: 15 Indie Games for the Holidays (Big Download Blog)