This question comes up a lot.
I would recommend either the Arboretum area (183 (Research) & 360 (Capital of Texas)) or the Domain area (Loop1 (mopac) and 360 (Capital of Texas)).
Some traveling ladies stay in the I35 & 290 area, there a couple decent hotels there but some of them are kinda sketchy.
Downtown has some nice Hotels but can be a hassle as far as parking and traffic.
Here is a link to a previous thread about the same subject, it has other links to even more similar threads.
http://www.eccie.net/showthread.php?...=best+location
Have a nice visit!