I'll take a crack at it :
I don't do Mythbuntu myself so it's even better when no OS cost is involved...
These are the parts I either have/had or heard good things about...
I have this case - Apex DM-317 mATX HTPC Case Silver Black 1X5.25 1X3.5 1X3.5INT 275W Low Profile Front Firewire - $45. The only 'complaint' I have is the 2 SATA plugs from the PSU are close together and would not plug into the DVD and the HDD if the HDD is at the bottom. An adapter is needed but I have tons of those around.
Mobo : Gigabyte GAMA780GM-S2H ($70), or the Nvidia equivalent like 8300GS IGP. Get whichever one best for Ubuntu OS if that's what you'll be using.
CPU : Athlon x2 5050e ($75)
HDD : anything equal or larger than 1TB (1TB can be had for $80, 1.5TB = $130). I won't recommend too many HDD for SFF cases so go big and you won't regret.
RAM : 4GB anything DDR2 800MHz for $35 after MIR
DVD Writer - any black one, I prefer LG or Samsung myself. ($30)
TV card : Hauppauge HVR-1250 ($65), comes with low profile bracket that will work with the above case. If dual tuner is required, I'd get the HVR-2250 for $160 then. The HVR-1250 is good enough for SD when paired with a CPU like the 2.7GHz dual core 5050e. Remotes are included, which I can only comment they work pretty well for Vista MC though a $30 Vista Remote is better.
Wireless KB/Mouse : $30, I may even look at the refurb higher end ones at Factory Direct or Canada Computers for about the same $ but don't spend over $50 for a set of input devices for crying out loud.
Others : internal card reader ($15), low profile video card (ATI4350 low profile is $30 after $10MIR), Vista Premium 64-bit upgradable to Window 7 ($125)
Total : $45+70+75+$80+$40+$30+$65+$30=$435 for 1TB HDD and HVR-1250; or $580 if opt for 1.5TB HDD and the HVR-2250.
Last edited by 57; 2009-08-09 at 03:02 PM.
Reason: Retail links removed.