you would probably get good input from C&V
A couple of considerations:
do you care if it is lugged or welded?
do you care if the fork is steel or carbon
What are you going to use the bike for?
Fast road, touring, commuting?
what type of components are you thinking? single speed/fixie, derailer, Internal gear?
My opinion/recommendation/rant is to consider drop bars.....they are far more versatile than pure flat bars. personally flat, straight bars cause me pain
understand that building is likely to be more expensive than buying a complete bike, unless you have a big parts bin
Some frame ideas for you:
used frame (miyata, panasonic, centurion, bridgestone are good quality 80's/90's frame to look for)
Surly
cross check (cyclo cross, well regarded for overall use)
Cross-Check | Bikes | Surly Bikes
pacer (road)
Pacer | Bikes | Surly Bikes
long haul trucker (touring, well regarded general use and commuting)
Long Haul Trucker | Bikes | Surly Bikes
soma
double cross (cyclocross, versatile)
Double Cross | SOMA Fabrications
san marcos (very nice frame general use/road designed by Grant petersen of Rivendell)
San Marcos Frame Set | SOMA Fabrications
stanyan (nice lugged road frame)
Stanyan Frame Set | SOMA Fabrications
wraith
this is a robbietunes best value frame ($1090...not $300 as I posted)
Pre-Order No.2 : The Hustle, Road | Wraith Fabrication