$ sqlplus "/as sysdba"

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL> select * from sm$ts_used;

TABLESPACE_NAME                     BYTES
------------------------------ ----------
SYSTEM                          510197760
USERS                             3080192
TBS_1                              196608
SYSAUX                          433586176
EXAMPLE                          79953920
UNDOTBS1                         17104896

6 rows selected.

SQL> select * from sm$ts_free;

TABLESPACE_NAME                     BYTES
------------------------------ ----------
SYSTEM                            3538944
USERS                             2097152
TBS_1                           104660992
SYSAUX                            6750208
EXAMPLE                          77266944
UNDOTBS1                        203030528
TBS_2                           104792064

7 rows selected.

SQL> select text from dba_views where view_name='SM$TS_USED';

TEXT
--------------------------------------------------------------------------------
select tablespace_name, sum(bytes) bytes from dba_segments
    group by tablespace_name

SQL> select text from dba_views where view_name='SM$TS_FREE';

TEXT
--------------------------------------------------------------------------------
select tablespace_name, sum(bytes) bytes from dba_free_space
    group by tablespace_name