Haven't seen this posted yet this offseason so here goes. Here's a list compiled from overthecap.com and ranked by cap space. Seattle comes in at #9, so a fair amount of cap space available, comparatively. That said, there's a good number of teams bunched around the Seahawks.
Team Space
Ind $117,249,480
NYJ $93,837,909
Cle $82,527,741
Buf $79,440,419
Oak $71,354,069
Hou $65,467,417
SF $61,881,508
Sea $54,980,232
Dal $52,986,337
Cin $51,944,991
ARI $51,454,529
Ten $44,028,563
Den $41,342,666
GB $40,353,980
LAR $35,733,828
Det $32,971,167
KC $32,468,439
Bal $28,410,292
NYG $26,187,094
LAC $21,925,567
Was $21,560,242
NE $20,766,924
Pit $20,685,468
Car $19,114,965
ATL $18,291,812
NO $15,662,015
Mia $13,352,817
Chi $13,232,452
TB $12,193,360
Min $6,800,401
Jax -$1,555,778
Phi -$15,375,726
Team Space
Ind $117,249,480
NYJ $93,837,909
Cle $82,527,741
Buf $79,440,419
Oak $71,354,069
Hou $65,467,417
SF $61,881,508
Sea $54,980,232
Dal $52,986,337
Cin $51,944,991
ARI $51,454,529
Ten $44,028,563
Den $41,342,666
GB $40,353,980
LAR $35,733,828
Det $32,971,167
KC $32,468,439
Bal $28,410,292
NYG $26,187,094
LAC $21,925,567
Was $21,560,242
NE $20,766,924
Pit $20,685,468
Car $19,114,965
ATL $18,291,812
NO $15,662,015
Mia $13,352,817
Chi $13,232,452
TB $12,193,360
Min $6,800,401
Jax -$1,555,778
Phi -$15,375,726