Thanks, I love Tumblr! I made a list a while back of blogs on tumblr and elsewhere that I like. You can see that here. Most, if not all, sites listed are still active and even better than before.

The following are all on Tumblr.

Inspiring GIFs:

psykzz
xverdxse
xcopy
maxcapacity
surragateself
rednor
dvdp

Art:

homespungeometry (patterns)
dimensies (mandalas)
ryansalge (he can probably draw better than you!)
wowgreat (curated by Holger Lippmann)
W:Blut (curated by Frederik Vanhoutte)

Informative (math/science/etc.):

matthen (Matt Henderson is a Mathematica wizard!)
iomikron
sayitwithscience
spookyactioncollective

Misc.:
notationnotes (“An investigation of the relationship between sound and image.”)

These people write and post about you! I want to talk to them in real life:
s33
thanatesque
theuniverseworks

I hope others can enjoy these too. I may add more to this list when more blogs come to mind. There is so much i like on Tumblr that I may be developing ADD, but If you have a blog or know of a blog similar to these feel free to let me know!