Starting today you can license Virtual Earth UltraCam (proprietary) aerial photography without having to license the Virtual Earth platform. This is great for offline use, wrapping your own client or creating an interface that allows for deeper zooming than the VE platform does today. You can purchase the photography through 2 vendors - Mapmart and i-Cubed.
Of course ESRI users will probably prefer to use the ArcGIS Online service (given how easy it will be to integrate into your existing projects), but now everyone has the same access and the freedom to use any software (Photoshop, Illustrator, gvSIG, MapInfo, AutoCAD, etc) they wish.
The only caveat is that this is the UltraCam imagery, not everything so you may not have anything available if you live outside of 200+ cities that have coverage. Of course if you do have it available, then there isn’t anything better as UltraCam blows away everything else. Microsoft’s purchase of Vexcel has really been very smart for them and this is what you can do when you own the data. I can buy UltraCam imagery for Tempe, AZ for about $4,000 from MapMart.
You can’t afford one yourself, but you can use the data captured from it.