PostGIS 1.5.2rc120 Sep 2010
The PostGIS web site is temporarily down, but the project team is pushing ahead (belatedly) with the 1.5.2 release series in the meanwhile. The reason we are not waiting is the same reason we are belated: 1.5.2 is required to run with PostgreSQL 9.0, which was freshly released recently (we should have released 1.5.2 a couple months ago, really).
You can get the 1.5.2rc1 source code from the PostGIS issue tracking page and wiki: http://trac.osgeo.org/postgis
Please test and post any issues as tickets, we are aiming to drop a final release pretty quickly. Try to confine yourself to posting deal-breaker tickets only.