Best Chipset of 2008 so far?

Look for P35 boards, they are excellent, especially ASUS P5ke if you're into OCing. I'm not sure these boards offer integrated graphics though, but this can be easily solve by buying a cheap video card.

Unfortunately(for you) the best to say would be the new AMD chipset, the 780G. Not only that the integerated graphics OC almost 100% and bring very nice real life gains. They even were able to run HD video content with a sempron +3200. Now thats pretty amazing, especially for under $100. Literally this board is calling out your name to buy it as it fits exactly everything you want dead on(with the exception of being an intel dog). But lets be real and not let a name overcome the ruler of all, money...

G35 would be the best choice for Intel.
http://www.asus.com/products.aspx? [...] =11&l3=584
Not all that cheap where I live. Costs about the same as a P5K Premium
By being an Intel fanboy you limit yourself to an expensive motherboard.
I've built a cheap AMD HTPC 3 weeks ago for 380 EUR.
MB $100 http://www.newegg.com/Product/Prod [...] 6813128090
CPU $60: http://www.newegg.com/Product/Prod [...] 6819103243
RAM $26: http://www.newegg.com/Product/Prod [...] 6820145590
HDD $110: http://www.newegg.com/Product/Prod [...] 6822136218
CASE $45: http://www.newegg.com/Product/Prod [...] 6811119115
PSU $60: http://www.newegg.com/Product/Prod [...] 6817139003
Total: $401

You can also save about $50 if you buy this case psu combo :
http://www.newegg.com/Product/Prod [...] 6811119118

EDIT: changed the HDD to WD6400AAKS

The best motherboard chipset, by a huge margin, would be x38/48. By saying "with onboard graphics," you've just limited the choices to the oldest and worst chipsets. Unlike AMD, Intel just don't have half decent onboard graphics options available, thus, they don't make fool of themselves by putting such trash on higher end boards.

^There are. It's the "go with the cheapest components for boards with onboard graphics to save a $" philosophy of boardbuilders that's to blame.

Go with AMD's 780G spec power curcuit and even the 125W 9850 BE fits in perfectly.

@dagger : Why go for a X38 board in a HTPC? A P31 board + HD 3450 would do what he needs perfectly for half the cost.

GIGABYTE GA-MA78GM-S2H = $90
(GIGABYTE GA-P31-S3G = $65 ASUS EAH3450/HTP/256M = $25) = $90 intel equivalent of 780G